<PAGE>
                                                                     EXHIBIT 4.9

================================================================================

                               GUARANTEE AGREEMENT


                                     Between


                               F.N.B. CORPORATION
                                 (as Guarantor)


                                       and


                            WILMINGTON TRUST COMPANY
                             (as Guarantee Trustee)


                                   dated as of


                             ---------------, ------

================================================================================

<PAGE>

                               FNB CAPITAL TRUST I

            Certain Sections of this Guarantee Agreement relating to
                         Sections 310 through 318 of the
                          Trust Indenture Act of 1939:

<TABLE>
<CAPTION>
Trust Indenture                                                                             Guarantee Agreement
  Act Section                                                                                     Section
---------------                                                                             -------------------
<S>               <C>                                                                       <C>
Section 310       (a) (1)...............................................................       4.1 (a)
                  (a) (2)...............................................................       4.1 (a)
                  (a) (3)...............................................................       Not Applicable
                  (a) (4)...............................................................       Not Applicable
                  (b)...................................................................       2.8, 4.1 (c)
Section 311       (a)...................................................................       Not Applicable
                  (b)...................................................................       Not Applicable
Section 312       (a)...................................................................       2.2 (a)
                  (b)...................................................................       2.2 (b)
                  (c)...................................................................       Not Applicable
Section 313       (a)...................................................................       2.3
                  (a) (4)...............................................................       2.3
                  (b)...................................................................       2.3
                  (c)...................................................................       2.3
                  (d)...................................................................       2.3
Section 314       (a)...................................................................       2.4
                  (b)...................................................................       2.4
                  (c) (1)...............................................................       2.5
                  (c) (2)...............................................................       2.5
                  (c) (3)...............................................................       2.5
                  (e)...................................................................       1.1, 2.5, 3.2
Section 315       (a)...................................................................       3.1 (d)
                  (b)...................................................................       2.7
                  (c)...................................................................       3.1 (c)
                  (d)...................................................................       3.1 (d)
                  (e)...................................................................       Not Applicable
Section 316       (a)...................................................................       1.1, 2.6, 5.4
                  (a) (1) (A)...........................................................       5.4
                  (a) (1) (B)...........................................................       5.4
                  (a) (2)...............................................................       Not Applicable
                  (b)...................................................................       5.3
                  (c)...................................................................       Not Applicable
Section 317       (a) (1)...............................................................       Not Applicable
                  (a) (2)...............................................................       Not Applicable
                  (b)...................................................................       Not Applicable
Section 318       (a)...................................................................       2.1
</TABLE>

Note:    This reconciliation and tie shall not, for any purpose, be deemed to be
         a part of the Guarantee Agreement.
<PAGE>

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                               Page
                                                                                                               ----
<S>                        <C>                                                                                 <C>
ARTICLE I.                 DEFINITIONS
         Section 1.1.                Definitions..........................................................       2

ARTICLE II.                TRUST INDENTURE ACT
         Section 2.1.                Trust Indenture Act; Application.....................................       5
         Section 2.2.                List of Holders......................................................       5
         Section 2.3.                Reports by the Guarantee Trustee.....................................       6
         Section 2.4.                Periodic Reports to Guarantee
                                     Trustee..............................................................       6
         Section 2.5.                Evidence of Compliance with Conditions Precedent.....................       6
         Section 2.6.                Events of Default; Waiver............................................       6
         Section 2.7.                Event of Default; Notice.............................................       6
         Section 2.8.                Conflicting Interests................................................       7

ARTICLE III.               POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE
         Section 3.1.                Powers and Duties of the Guarantee Trustee...........................       7
         Section 3.2.                Certain Rights of Guarantee Trustee..................................       9
         Section 3.3.                Indemnity............................................................      10
         Section 3.4.                Expenses.............................................................      10

ARTICLE IV.                GUARANTEE TRUSTEE
         Section 4.1.                Guarantee Trustee; Eligibility.......................................      11
         Section 4.2.                Appointment, Removal and Resignation of the Guarantee Trustee........      11

ARTICLE V.                 GUARANTEE
         Section 5.1.                Guarantee............................................................      12
         Section 5.2.                Waiver of Notice and Demand..........................................      12
         Section 5.3.                Obligations Not Affected.............................................      12
         Section 5.4.                Rights of Holders....................................................      13
         Section 5.5.                Guarantee of Payment.................................................      14
         Section 5.6.                Subrogation..........................................................      14
         Section 5.7.                Independent Obligations..............................................      14

ARTICLE VI.                COVENANTS AND SUBORDINATION
         Section 6.1.                Subordination........................................................      14
         Section 6.2.                Pari Passu Guarantees................................................      14

ARTICLE VII.      TERMINATION
         Section 7.1                 Termination..........................................................      15
</TABLE>


                                        i
<PAGE>

<TABLE>
<S>                        <C>                                                                                  <C>
ARTICLE VIII.              MISCELLANEOUS
         Section 8.1.                Successors and Assigns...............................................      15
         Section 8.2.                Amendments...........................................................      15
         Section 8.3.                Notices..............................................................      16
         Section 8.4.                Benefit..............................................................      17
         Section 8.5.                Interpretation.......................................................      17
         Section 8.6.                Governing Law........................................................      17
         Section 8.7.                Counterparts.........................................................      18
</TABLE>


                                       ii
<PAGE>

                               GUARANTEE AGREEMENT

         THIS GUARANTEE AGREEMENT, dated as of __________, _____ (this
"Guarantee Agreement"), is executed and delivered by F.N.B. CORPORATION, a
Florida corporation (the "Guarantor"), having its principal office at 2150
Goodlette Road North, Naples, Florida 34102 and WILMINGTON TRUST COMPANY, a
Delaware banking corporation, having its principal office at Rodney Square
North, 1100 North Market Street, Wilmington, Delaware 19890-0001, as trustee,
for the benefit of the Holders (as defined herein) from time to time of the
Preferred Securities (as defined herein) of FNB Capital Trust I, a Delaware
statutory business trust (the "Issuer Trust").

                                    RECITALS

         WHEREAS, pursuant to an Amended and Restated Trust Agreement (the
"Trust Agreement"), dated as of __________, ____, among F.N.B. Corporation, as
Depositor, Wilmington Trust Company, as Property Trustee (the "Property
Trustee") and as Delaware Trustee (the "Delaware Trustee") (collectively, the
"Issuer Trustees") and the Holders from time to time of preferred undivided
beneficial ownership interests in the assets of the Issuer Trust, the Issuer
Trust is issuing up to $__________ aggregate Liquidation Amount (as defined
herein) (or $_____________ if the Underwriters exercise their over-allotment
option) of its _____% Preferred Securities, Liquidation Amount $____ per
preferred security (the "Preferred Securities"), representing preferred
undivided beneficial ownership interests in the assets of the Issuer Trust and
having the terms set forth in the Trust Agreement;

         WHEREAS, the Preferred Securities will be issued by the Issuer Trust
and the proceeds thereof, together with the proceeds from the issuance of the
Issuer Trust's Common Securities (as defined herein), will be used to purchase
the Junior Subordinated Debentures due __________, ____ (as defined in the Trust
Agreement) (the "Junior Subordinated Debentures") of the Guarantor which will be
deposited with Wilmington Trust Company, as Property Trustee under the Trust
Agreement, as trust assets; and

         WHEREAS, as incentive for the Holders to purchase the Preferred
Securities, the Guarantor desires irrevocably and unconditionally to agree, to
the extent set forth herein, to pay to the Holders of the Preferred Securities
the Guarantee Payments (as defined herein) and to make certain other payments on
the terms and conditions set forth herein.

         NOW, THEREFORE, in consideration of the purchase of the Preferred
Securities by each Holder, which purchase the Guarantor hereby acknowledges
shall benefit the Guarantor, and intending to be legally bound hereby, the
Guarantor executes and delivers this Guarantee Agreement for the benefit of the
Holders from time to time of the Preferred Securities.
<PAGE>

                                    ARTICLE I

                                   DEFINITIONS

Section 1.1.      Definitions.

         As used in this Guarantee Agreement, the terms set forth below shall,
unless the context otherwise requires, have the following meanings. Capitalized
terms used but not otherwise defined herein shall have the meanings assigned to
such terms in the Trust Agreement as in effect on the date hereof.

         "Additional Amount" has the meaning specified in the Trust Agreement.

         "Affiliate" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person. For the purposes of this definition,
"control" when used with respect to any specified Person means the power to
direct the management and policies of such Person, directly or indirectly,
whether through the ownership of voting securities, by contract or otherwise;
and the terms "controlling" and "controlled" have meanings correlative to the
foregoing.

         "Common Securities" means the securities representing common undivided
beneficial interests in the assets of the Issuer Trust.

         "Delaware Trustee" shall have the meaning specified in the first
recital of this Guarantee Agreement.

         "Distributions" means preferential cumulative cash distributions
accumulating from ___________, ____ and payable quarterly in arrears on March
31, June 30, September 30, and December 31 of each year, commencing ___________,
_____ at the annual rate of ____% of the Liquidation Amount.

         "Event of Default" means (a) a default by the Guarantor in any of its
payment obligations under this Guarantee Agreement, or (b) a default by the
Guarantor in any other obligation hereunder that remains unremedied for 30 days.

         "Guarantee Agreement" means this Guarantee Agreement, as modified,
amended or supplemented from time to time.

         "Guarantee Payments" means the following payments or distributions,
without duplication, with respect to the Preferred Securities, to the extent not
paid or made by or on behalf of the Issuer Trust: (a) any accrued and unpaid
Distributions (as defined in the Trust Agreement) required to be paid on the
Preferred Securities, to the extent the Issuer Trust shall have funds on hand
available therefor at such time, (b) the Redemption Price, with respect to the
Preferred Securities called for redemption by the Issuer Trust to the extent
that the Issuer Trust shall have funds on hand available therefor at such time,
and (c) upon a voluntary or involuntary termination, winding-up or liquidation
of the Issuer Trust, unless the Junior Subordinated


                                       2
<PAGE>

Debentures are distributed to the Holders, the lesser of (i) the aggregate of
the Liquidation Amount and all accumulated and unpaid Distributions to the date
of payment to the extent the Issuer Trust shall have funds on hand available to
make such payment at such time and (ii) the amount of assets of the Issuer Trust
remaining available for distribution to Holders in liquidation of the Issuer
Trust (in either case, the "Liquidation Distribution").

         "Guarantee Trustee" means Wilmington Trust Company, until a Successor
Guarantee Trustee has been appointed and has accepted such appointment pursuant
to the terms of this Guarantee Agreement and thereafter means each such
Successor Guarantee Trustee.

         "Guarantor" shall have the meaning specified in the preamble of this
Guarantee Agreement.

         "Holder" means any holder, as registered on the books and records of
the Issuer Trust, of any Preferred Securities; provided, however, that, in
determining whether the holders of the requisite percentage of Preferred
Securities have given any request, notice, consent or waiver hereunder, "Holder"
shall not include the Guarantor, the Guarantee Trustee, or any Affiliate of the
Guarantor or the Guarantee Trustee.

         "Indenture" means the Junior Subordinated Indenture dated as of
__________, ____, between F.N.B. Corporation and Wilmington Trust Company, as
trustee, as may be modified, amended or supplemented from time to time.

         "Issuer Trust" shall have the meaning specified in the preamble of this
Guarantee Agreement.

         "Issuer Trustees" shall have the meaning specified in the first recital
of this Guarantee Agreement.

         "Junior Subordinated Debentures" shall have the meaning specified in
the first recital of this Guarantee Agreement.

         "Like Amount" means (a) with respect to a redemption of Preferred
Securities, Preferred Securities having a Liquidation Amount equal to the
principal amount of Junior Subordinated Debentures to be contemporaneously
redeemed in accordance with the Indenture, the proceeds of which will be used to
pay the Redemption Price of such Preferred Securities, (b) with respect to a
distribution of Junior Subordinated Debentures to Holders of Preferred
Securities in connection with a dissolution or liquidation of the Issuer Trust,
Junior Subordinated Debentures having a principal amount equal to the
Liquidation Amount of the Preferred Securities of the Holder to whom such Junior
Subordinated Debentures are distributed, and (c) with respect to any
distribution of an Additional Amount to Holders of Preferred Securities, Junior
Subordinated Debentures having a principal amount equal to the Liquidation
Amount of the Preferred Securities in respect of which such distribution is
made.

         "Liquidation Amount" means the stated amount of $______ per Preferred
Security.


                                       3
<PAGE>

         "Majority in Liquidation Amount of the Preferred Securities" means,
except as provided by the Trust Indenture Act, Preferred Securities representing
more than 50% of the aggregate Liquidation Amount of all then outstanding
Preferred Securities issued by the Issuer Trust.

         "Officers' Certificate" means, with respect to any Person, a
certificate signed by the Chief Executive Officer or President, and by the Chief
Financial Officer, Treasurer, the Secretary or an Assistant Secretary of such
Person, and delivered to the Guarantee Trustee. Any Officers' Certificate
delivered with respect to compliance with a condition or covenant provided for
in this Guarantee Agreement shall include:

                  (a)      a statement by each officer signing the Officers'
Certificate that such officer has read the covenant or condition and the
definitions relating thereto;

                  (b)      a brief statement of the nature and scope of the
examination or investigation undertaken by such officer in rendering the
Officers' Certificate;

                  (c)      a statement that such officer has made such
examination or investigation as, in such officer's opinion, is necessary to
enable such officer to express an informed opinion as to whether or not such
covenant or condition has been complied with; and

                  (d)      a statement as to whether, in the opinion of such
officer, such condition or covenant has been complied with.

         "Person" means a legal person, including any individual, corporation,
estate, partnership, joint venture, association, joint stock company, limited
liability company, trust, unincorporated association, or government or any
agency or political subdivision thereof, or any other entity of whatever nature.

         "Preferred Securities" shall have the meaning specified in the first
recital of this Guarantee Agreement.

         "Property Trustee" shall have the meaning specified in the first
recital of this Guarantee Agreement.

         "Redemption Date" means, with respect to any Preferred Security to be
redeemed, the date fixed for such redemption by or pursuant to the Trust
Agreement; provided that each Junior Subordinated Debenture Redemption Date (as
such term is defined in the Indenture) and the stated maturity of the Junior
Subordinated Debentures shall be a Redemption Date for a Like Amount of
Preferred Securities.

         "Redemption Price" shall have the meaning specified in the Trust
Agreement.

         "Responsible Officer" means, when used with respect to the Guarantee
Trustee, any officer assigned to the Corporate Trust Office, including any
managing director, principal, vice president, assistant vice president,
assistant treasurer, assistant secretary or any other officer of the Guarantee
Trustee customarily performing functions similar to those performed by any of
the


                                       4
<PAGE>

above designated officers and having direct responsibility for the
administration of this Guarantee Agreement, and also, with respect to a
particular matter, any other officer to whom such matter is referred because of
such officer's knowledge of and familiarity with the particular subject.

         "Senior Indebtedness" shall have the meaning specified in the
Indenture.

         "Successor Guarantee Trustee" means a successor Guarantee Trustee
possessing the qualifications to act as Guarantee Trustee under Section 4.1.

         "Trust Agreement" shall have the meaning specified in the Recitals to
this Guarantee Agreement.

         "Trust Indenture Act" means the Trust Indenture Act of 1939, as amended
by the Trust Indenture Reform Act of 1990, or any successor statute, in each
case as amended from time to time.

                                   ARTICLE II

                               TRUST INDENTURE ACT

Section 2.1.      Trust Indenture Act; Application.

         If any provision hereof limits, qualifies or conflicts with a provision
of the Trust Indenture Act that is required to be a part of and govern this
Guarantee Agreement, the provision of the Trust Indenture Act shall control. If
any provision of this Guarantee Agreement modifies or excludes any provision of
the Trust Indenture Act that may be so modified or excluded, the latter
provision shall be deemed to apply to this Guarantee Agreement as so modified or
excluded, as the case may be.

Section 2.2.      List of Holders.

         (a)      The Guarantor will furnish or cause to be furnished to the
Guarantee Trustee:

                  (i)      quarterly, not more than 15 days after March 15, June
         15, September 15 and December 15 in each year, a list, in such form as
         the Guarantee Trustee may reasonably require, of the names and
         addresses of the Holders as of such date; and

                  (ii)     at such other times as the Guarantee Trustee may
         request in writing, within 30 days after the receipt by the Guarantor
         of any such request, a list of similar form and content as of a date
         not more than 15 days prior to the time such list is furnished.

         (b)      The Guarantee Trustee shall comply with the requirements of
Section 312(b) of the Trust Indenture Act.


                                       5
<PAGE>

Section 2.3.      Reports by the Guarantee Trustee.

         Within 60 days of January 31 of each year commencing _________, ____,
the Guarantee Trustee shall provide to the Holders such reports, if any, as are
required by Section 313 of the Trust Indenture Act in the form and in the manner
provided by Section 313 of the Trust Indenture Act. The Guarantee Trustee shall
also comply with the requirements of Section 313(d) of the Trust Indenture Act.

Section 2.4.      Periodic Reports to the Guarantee Trustee.

         The Guarantor shall provide to the Guarantee Trustee and the Holders
such documents, reports and information, if any, as required by Section 314 of
the Trust Indenture Act and the compliance certificate required by Section 314
of the Trust Indenture Act, in the form, in the manner and at the times required
by Section 314 of the Trust Indenture Act.

Section 2.5.      Evidence of Compliance with Conditions Precedent.

         The Guarantor shall provide to the Guarantee Trustee such evidence of
compliance with such conditions precedent, if any, provided for in this
Guarantee Agreement that relate to any of the matters set forth in Section
314(c) of the Trust Indenture Act. Any certificate or opinion required to be
given by an officer pursuant to Section 314(c)(1) may be given in the form of an
Officers' Certificate.

Section 2.6.      Events of Default; Waiver.

         The Holders of a Majority in Liquidation Amount of the Preferred
Securities may, by vote, on behalf of the Holders, waive any past Event of
Default and its consequences. Upon such waiver, any such Event of Default shall
cease to exist, and any Event of Default arising therefrom shall be deemed to
have been cured, for every purpose of this Guarantee Agreement, but no such
waiver shall extend to any subsequent or other default or Event of Default or
impair any right consequent therefrom.

Section 2.7.      Event of Default; Notice.

         (a)      The Guarantee Trustee shall, within 90 days after the
occurrence of an Event of Default, transmit by mail, first class postage
prepaid, to the Holders, notices of all Events of Default known to the Guarantee
Trustee, unless such Events of Default have been cured before the giving of such
notice; provided that, except in the case of a default in the payment of a
Guarantee Payment, the Guarantee Trustee shall be protected in withholding such
notice if and so long as the Board of Directors, the executive committee or a
trust committee of directors and/or Responsible Officers of the Guarantee
Trustee in good faith determines that the withholding of such notice is in the
interests of the Holders.

         (b)      The Guarantee Trustee shall not be deemed to have knowledge of
any Event of Default unless (i) a Responsible Officer charged with the
administration of this Guarantee Agreement shall have received written notice of
such Event of Default, or (ii) a Responsible


                                       6
<PAGE>

Officer of the Guarantee Trustee charged with administration of the Trust
Agreement shall have obtained actual knowledge thereof.

Section 2.8.      Conflicting Interests.

         The Trust Agreement shall be deemed to be specifically described in
this Guarantee Agreement for the purposes of clause (i) of the first proviso
contained in Section 310(b) of the Trust Indenture Act.

                                   ARTICLE III

                        POWERS, DUTIES AND RIGHTS OF THE
                                GUARANTEE TRUSTEE

Section 3.1.      Powers and Duties of the Guarantee Trustee.

         (a)      This Guarantee Agreement shall be held by the Guarantee
Trustee for the benefit of the Holders, and the Guarantee Trustee shall not
transfer this Guarantee Agreement to any Person except to a Holder exercising
his or her rights pursuant to Section 5.4(d) or to a Successor Guarantee Trustee
on acceptance by such Successor Guarantee Trustee of its appointment to act as
Successor Guarantee Trustee hereunder. The right, title and interest of the
Guarantee Trustee, as such, hereunder shall automatically vest in any Successor
Guarantee Trustee, upon acceptance by such Successor Guarantee Trustee of its
appointment hereunder, and such vesting and cessation of title shall be
effective whether or not conveyancing documents have been executed and delivered
pursuant to the appointment of such Successor Guarantee Trustee.

         (b)      If an Event of Default has occurred and is continuing, the
Guarantee Trustee shall enforce this Guarantee Agreement for the benefit of the
Holders.

         (c)      The Guarantee Trustee, before the occurrence of any Event of
Default and after the curing of all Events of Default that may have occurred,
shall be obligated to perform only such duties as are specifically set forth in
this Guarantee Agreement (including pursuant to Section 2.1), and no implied
covenants shall be read into this Guarantee Agreement against the Guarantee
Trustee. If an Event of Default has occurred (that has not been cured or waived
pursuant to Section 2.6), the Guarantee Trustee shall exercise such of the
rights and powers vested in it by this Guarantee Agreement, and use the same
degree of care and skill in its exercise thereof, as a prudent person would
exercise or use under the circumstances in the conduct of his or her own
affairs.


                                       7
<PAGE>

         (d)      No provision of this Guarantee Agreement shall be construed to
relieve the Guarantee Trustee from liability for its own negligent action, its
own negligent failure to act or its own bad faith or willful misconduct, except
that:

                  (i)      prior to the occurrence of any Event of Default and
         after the curing or waiving of all such Events of Default that may have
         occurred:

                           (A)      the duties and obligations of the Guarantee
                  Trustee shall be determined solely by the express provisions
                  of this Guarantee Agreement (including pursuant to Section
                  2.1), and the Guarantee Trustee shall not be liable except for
                  the performance of such duties and obligations as are
                  specifically set forth in this Guarantee Agreement (including
                  pursuant to Section 2.1); and

                           (B)      in the absence of bad faith on the part of
                  the Guarantee Trustee, the Guarantee Trustee may conclusively
                  rely, as to the truth of the statements and the correctness of
                  the opinions expressed therein, upon any certificates or
                  opinions furnished to the Guarantee Trustee and conforming to
                  the requirements of this Guarantee Agreement; but in the case
                  of any such certificates or opinions that by any provision
                  hereof or of the Trust Indenture Act are specifically required
                  to be furnished to the Guarantee Trustee, the Guarantee
                  Trustee shall be under a duty to examine the same to determine
                  whether or not they conform to the requirements of this
                  Guarantee Agreement;

                  (ii)     the Guarantee Trustee shall not be liable for any
         error of judgment made in good faith by a Responsible Officer of the
         Guarantee Trustee, unless it shall be proved that the Guarantee Trustee
         was negligent in ascertaining the pertinent facts upon which such
         judgment was made;

                  (iii)    the Guarantee Trustee shall not be liable with
         respect to any action taken or omitted to be taken by it in good faith
         in accordance with the direction of the Holders of not less than a
         Majority in Liquidation Amount of the Preferred Securities relating to
         the time, method and place of conducting any proceeding for any remedy
         available to the Guarantee Trustee, or exercising any trust or power
         conferred upon the Guarantee Trustee under this Guarantee Agreement;
         and

                  (iv)     no provision of this Guarantee Agreement shall
         require the Guarantee Trustee to expend or risk its own funds or
         otherwise incur personal financial liability in the performance of any
         of its duties or in the exercise of any of its rights or powers if the
         Guarantee Trustee shall have reasonable grounds for believing that the
         repayment of such funds or liability is not assured to it under the
         terms of this Guarantee Agreement or adequate indemnity against such
         risk or liability is not reasonably assured to it.


                                       8
<PAGE>

Section 3.2.      Certain Rights of Guarantee Trustee.

         (a)      Subject to the provisions of Section 3.1:

                  (i)      the Guarantee Trustee may conclusively rely and shall
         be fully protected in acting or refraining from acting upon any
         resolution, certificate, statement, instrument, opinion, report,
         notice, request, direction, consent, order, bond, debenture, note,
         other evidence of indebtedness or other paper or document reasonably
         believed by it to be genuine and to have been signed, sent or presented
         by the proper party or parties;

                  (ii)     any direction or act of the Guarantor contemplated by
         this Guarantee Agreement shall be sufficiently evidenced by an
         Officers' Certificate unless otherwise prescribed herein;

                  (iii)    whenever, in the administration of this Guarantee
         Agreement, the Guarantee Trustee shall deem it desirable that a matter
         be proved or established before taking, suffering or omitting to take
         any action hereunder, the Guarantee Trustee (unless other evidence is
         herein specifically prescribed) may, in the absence of bad faith on its
         part, request and conclusively rely upon an Officers' Certificate
         which, upon receipt of such request from the Guarantee Trustee, shall
         be promptly delivered by the Guarantor;

                  (iv)     the Guarantee Trustee may consult with legal counsel,
         and the written advice or opinion of such legal counsel with respect to
         legal matters shall be full and complete authorization and protection
         in respect of any action taken, suffered or omitted to be taken by it
         hereunder in good faith and in accordance with such advice or opinion.
         Such legal counsel may be legal counsel to the Guarantor or any of its
         Affiliates and may be one of its employees. The Guarantee Trustee shall
         have the right at any time to seek instructions concerning the
         administration of this Guarantee Agreement from any court of competent
         jurisdiction;

                  (v)      the Guarantee Trustee shall be under no obligation to
         exercise any of the rights or powers vested in it by this Guarantee
         Agreement at the request or direction of any Holder, unless such Holder
         shall have provided to the Guarantee Trustee such security and
         indemnity as would satisfy a reasonable person in the position of the
         Guarantee Trustee, against the costs, expenses (including attorneys'
         fees and expenses) and liabilities that might be incurred by it in
         complying with such request or direction, including such reasonable
         advances as may be requested by the Guarantee Trustee; provided,
         however, that nothing herein shall relieve the Guarantee Trustee of its
         obligations upon the occurrence of an Event of Default that has not
         been cured or waived to exercise the rights and powers vested in the
         Guarantee Trustee by this Guarantee, and to use the same degree of care
         and skill in exercising such rights and powers as a reasonably prudent
         person would use under the circumstances in the conduct of his own
         affairs;

                  (vi)     the Guarantee Trustee shall not be bound to make any
         investigation into the facts or matters stated in any resolution,
         certificate, statement, instrument, opinion,


                                       9
<PAGE>

         report, notice, request, direction, consent, order, bond, debenture,
         note, other evidence of indebtedness or other paper or document, but
         the Guarantee Trustee, in its discretion, may make such further inquiry
         or investigation into such facts or matters as it may see fit;

                  (vii)    the Guarantee Trustee may execute any of the trusts
         or powers hereunder or perform any duties hereunder either directly or
         by or through its agents or attorneys, and the Guarantee Trustee shall
         not be responsible for any negligence or willful misconduct on the part
         of any such agent or attorney appointed with due care by it hereunder.
         Nothing herein shall be construed as limiting or restricting the right
         of the Guarantor to bring any action directly against any agent or
         attorney appointed by the Guarantee Trustee for any negligence or
         willful misconduct on the part of such agent or attorney; and

                  (viii)   whenever in the administration of this Guarantee
         Agreement the Guarantee Trustee shall deem it desirable to receive
         instructions with respect to enforcing any remedy or right or taking
         any other action hereunder, the Guarantee Trustee (A) may request
         instructions from the Holders, (B) may refrain from enforcing such
         remedy or right or taking such other action until such instructions are
         received and (C) shall be fully protected in acting in accordance with
         such instructions.

         (b)      No provision of this Guarantee Agreement shall be deemed to
impose any duty or obligation on the Guarantee Trustee to perform any act or
acts or exercise any right, power, duty or obligation conferred or imposed on it
in any jurisdiction in which it shall be illegal, or in which the Guarantee
Trustee shall be unqualified or incompetent in accordance with applicable law,
to perform any such act or acts or to exercise any such right, power, duty or
obligation. No permissive power or authority available to the Guarantee Trustee
shall be construed to be a duty to act in accordance with such power and
authority.

Section 3.3.      Indemnity.

         The Guarantor agrees to indemnify the Guarantee Trustee (which for
purposes of this Section 3.3 shall include its directors, officers, employees
and agents) for, and to hold the Guarantee Trustee harmless against, any loss,
liability or expense incurred without negligence, willful misconduct or bad
faith on the part of the Guarantee Trustee, arising out of or in connection with
the acceptance or administration of this Guarantee Agreement, including the
reasonable costs and expenses of defending against any claim or liability in
connection with the exercise or performance of any of its powers or duties
hereunder. The provisions of this Section 3.3 shall survive the payment in full
of the Preferred Securities or the resignation or removal of the Guarantor
Trustee for a period equal to the statute of limitations applicable to a claim
based hereon.

Section 3.4.      Expenses.

         The Guarantor shall from time to time reimburse the Guarantee Trustee
for its reasonable expenses and costs (including reasonable attorneys' or
agents' fees) incurred in connection with the performance of its duties
hereunder.


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<PAGE>

                                   ARTICLE IV

                                GUARANTEE TRUSTEE

Section 4.1.      Guarantee Trustee; Eligibility.

         (a)      There shall at all times be a Guarantee Trustee which shall:

                  (i)      not be an Affiliate of the Guarantor; and

                  (ii)     be a Person that is eligible pursuant to the Trust
         Indenture Act to act as such and has a combined capital and surplus of
         at least $50,000,000, and shall be a corporation meeting the
         requirements of Section 310(a) of the Trust Indenture Act. If such
         corporation publishes reports of condition at least annually, pursuant
         to law or to the requirements of the supervising or examining
         authority, then, for the purposes of this Section and to the extent
         permitted by the Trust Indenture Act, the combined capital and surplus
         of such corporation shall be deemed to be its combined capital and
         surplus as set forth in its most recent report of condition so
         published.

         (b)      If at any time the Guarantee Trustee shall cease to be
eligible to so act under Section 4.1(a), the Guarantee Trustee shall immediately
resign in the manner and with the effect set out in Section 4.2(b).

         (c)      If the Guarantee Trustee has or shall acquire any "conflicting
interest" within the meaning of Section 310(b) of the Trust Indenture Act, the
Guarantee Trustee and Guarantor shall in all respects comply with the provisions
of Section 310(b) of the Trust Indenture Act.

Section 4.2.      Appointment, Removal and Resignation of the Guarantee Trustee.

         (a)      No resignation or removal of the Guarantee Trustee and no
appointment of a Successor Guarantee Trustee pursuant to this Article IV shall
become effective until the acceptance of appointment by the Successor Guarantee
Trustee by written instrument executed by the Successor Guarantee Trustee and
delivered to the Holders and the Guarantee Trustee.

         (b)      Subject to Section 4.2(a), a Guarantee Trustee may resign at
any time by giving written notice thereof to the Holders. The Guarantor shall
appoint a successor by requesting from at least three Persons meeting the
eligibility requirements such Person's expenses and charges to serve as the
Guarantee Trustee, and selecting the Person who agrees to the lowest expenses
and charges. If the instrument of acceptance by the Successor Guarantee Trustee
shall not have been delivered to the Guarantee Trustee within 60 days after the
giving of such notice of resignation, the Guarantee Trustee may petition, at the
expense of the Guarantor, any court of competent jurisdiction for the
appointment of a Successor Guarantee Trustee.


                                       11
<PAGE>

         (c)      The Guarantee Trustee may be removed for cause at any time by
Act (within the meaning of Section 608 of the Trust Agreement) of the Holders of
at least a Majority in Liquidation Amount of the Preferred Securities, delivered
to the Guarantee Trustee.

         (d)      If the Guarantor shall fail to appoint a Successor Guarantor
Trustee, or if a Guarantee Trustee shall be removed or become incapable of
acting as Guarantee Trustee, or if any vacancy shall occur in the office of any
Guarantee Trustee for any cause, the Holders of the Preferred Securities, by Act
of the Holders of record of not less than 25% in aggregate Liquidation Amount of
the Preferred Securities then outstanding delivered to such Guarantee Trustee,
shall promptly appoint a successor Guarantee Trustee. If no Successor Guarantee
Trustee shall have been so appointed by the Holders of the Preferred Securities
and such appointment accepted by the Successor Guarantee Trustee, any Holder, on
behalf of himself and all others similarly situated, may petition any court of
competent jurisdiction for the appointment of a Successor Guarantee Trustee.

                                    ARTICLE V

                                    GUARANTEE

Section 5.1.      Guarantee.

         The Guarantor irrevocably and unconditionally agrees to pay in full on
a subordinated basis as set forth in Section 6.1 hereof to the Holders the
Guarantee Payments (without duplication of amounts theretofore paid by or on
behalf of the Issuer Trust), as and when due, regardless of any defense, right
of set-off or counterclaim which the Issuer Trust may have or assert, except the
defense of payment. The Guarantor's obligation to make a Guarantee Payment may
be satisfied by direct payment of the required amounts by the Guarantor to the
Holders or by causing the Issuer Trust to pay such amounts to the Holders. The
Guarantor shall give prompt written notice to the Guarantee Trustee in the event
it makes any direct payment hereunder.

Section 5.2.      Waiver of Notice and Demand.

         The Guarantor hereby waives notice of acceptance of the Guarantee
Agreement and of any liability to which it applies or may apply, presentment,
demand for payment, any right to require a proceeding first against the
Guarantee Trustee, the Issuer Trust or any other Person before proceeding
against the Guarantor, protest, notice of nonpayment, notice of dishonor, notice
of redemption and all other notices and demands.


                                       12
<PAGE>

Section 5.3.      Obligations Not Affected.

         The obligations, covenants, agreements and duties of the Guarantor
under this Guarantee Agreement shall in no way be affected or impaired by reason
of the happening from time to time of any of the following:

         (a)      the release or waiver, by operation of law or otherwise, of
the performance or observance by the Issuer Trust of any express or implied
agreement, covenant, term or condition relating to the Preferred Securities to
be performed or observed by the Issuer Trust;

         (b)      the extension of time for the payment by the Issuer Trust of
all or any portion of the Distributions (other than an extension of time for
payment of Distributions that results from the extension of any interest payment
period on the Junior Subordinated Debentures as so provided in the Indenture),
Redemption Price, Liquidation Distribution or any other sums payable under the
terms of the Preferred Securities or the extension of time for the performance
of any other obligation under, arising out of, or in connection with, the
Preferred Securities;

         (c)      any failure, omission, delay or lack of diligence on the part
of the Holders to enforce, assert or exercise any right, privilege, power or
remedy conferred on the Holders pursuant to the terms of the Preferred
Securities, or any action on the part of the Issuer Trust granting indulgence or
extension of any kind;

         (d)      the voluntary or involuntary liquidation, dissolution, sale of
any collateral, receivership, insolvency, bankruptcy, assignment for the benefit
of creditors, reorganization, arrangement, composition or readjustment of debt
of, or other similar proceedings affecting, the Issuer Trust or any of the
assets of the Issuer Trust;

         (e)      any invalidity of, or defect or deficiency in, the Preferred
Securities;

         (f)      the settlement or compromise of any obligation guaranteed
hereby or hereby incurred; or

         (g)      any other circumstance whatsoever that might otherwise
constitute a legal or equitable discharge or defense of a guarantor (other than
payment of the underlying obligation), it being the intent of this Section 5.3
that the obligations of the Guarantor hereunder shall be absolute and
unconditional under any and all circumstances.

         There shall be no obligation of the Holders to give notice to, or
obtain the consent of, the Guarantor with respect to the happening of any of the
foregoing.

Section 5.4.      Rights of Holders.

         The Guarantor expressly acknowledges that: (a) this Guarantee Agreement
will be deposited with the Guarantee Trustee to be held for the benefit of the
Holders; (b) the Guarantee Trustee has the right to enforce this Guarantee
Agreement on behalf of the Holders; (c) the Holders of a Majority in Liquidation
Amount of the Preferred Securities have the right to direct


                                       13
<PAGE>

the time, method and place of conducting any proceeding for any remedy available
to the Guarantee Trustee in respect of this Guarantee Agreement or exercising
any trust or power conferred upon the Guarantee Trustee under this Guarantee
Agreement; and (d) any Holder may institute a legal proceeding directly against
the Guarantor to enforce its rights under this Guarantee Agreement, without
first instituting a legal proceeding against the Guarantee Trustee, the Issuer
Trust or any other Person.

Section 5.5.      Guarantee of Payment.

         This Guarantee Agreement creates a guarantee of payment and not of
collection. This Guarantee Agreement will not be discharged except by payment of
the Guarantee Payments in full (without duplication of amounts theretofore paid
by the Issuer Trust) or upon the distribution of Junior Subordinated Debentures
to Holders as provided in the Trust Agreement.

Section 5.6.      Subrogation.

         The Guarantor shall be subrogated to all rights (if any) of the Holders
against the Issuer Trust in respect of any amounts paid to the Holders by the
Guarantor under this Guarantee Agreement; provided, however, that the Guarantor
shall not (except to the extent required by mandatory provisions of law) be
entitled to enforce or exercise any rights which it may acquire by way of
subrogation or any indemnity, reimbursement or other agreement, in all cases as
a result of payment under this Guarantee Agreement, if at the time of any such
payment, any amounts are due and unpaid under this Guarantee Agreement. If any
amount shall be paid to the Guarantor in violation of the preceding sentence,
the Guarantor agrees to hold such amount in trust for the Holders and to pay
over such amount to the Holders.

Section 5.7.      Independent Obligations.

         The Guarantor acknowledges that its obligations hereunder are
independent of the obligations of the Issuer Trust with respect to the Preferred
Securities and that the Guarantor shall be liable as principal and as debtor
hereunder to make Guarantee Payments pursuant to the terms of this Guarantee
Agreement notwithstanding the occurrence of any event referred to in subsections
(a) through (g), inclusive, of Section 5.3 hereof.

                                   ARTICLE VI

                          COVENANTS AND SUBORDINATION

Section 6.1.      Subordination.

         This Guarantee Agreement will constitute an unsecured obligation of the
Guarantor and will rank subordinate and junior in right of payment to all Senior
Indebtedness of the Guarantor to the extent and in the manner set forth in the
Indenture with respect to the Junior Subordinated Debentures, and the provisions
of Article XVI of the Indenture will apply, mutatis mutandis, to the obligations
of the Guarantor hereunder. The obligations of the Guarantor hereunder do not
constitute Senior Indebtedness of the Guarantor.


                                       14
<PAGE>

Section 6.2.      Pari Passu Guarantees.

         The obligations of the Guarantor under this Guarantee Agreement shall
rank pari passu with any similar guarantee agreements issued by the Guarantor on
behalf of the holders of preferred or capital securities issued by the Issuer
Trust and with any other security, guarantee or other obligation that is
expressly stated to rank pari passu with the obligations of the Guarantor under
this Guarantee Agreement.

                                   ARTICLE VII

                                   TERMINATION

Section 7.1.      Termination.

         This Guarantee Agreement shall terminate and be of no further force and
effect upon (a) full payment of the Redemption Price of all Preferred
Securities, (b) the distribution of Junior Subordinated Debentures to the
Holders in exchange for all of the Preferred Securities or (c) full payment of
the amounts payable in accordance with Article IX of the Trust Agreement upon
liquidation of the Issuer Trust. Notwithstanding the foregoing, this Guarantee
Agreement will continue to be effective or will be reinstated, as the case may
be, if at any time any Holder is required to repay any sums paid with respect to
the Preferred Securities or this Guarantee Agreement.

                                  ARTICLE VIII

                                  MISCELLANEOUS

Section 8.1.      Successors and Assigns.

         All guarantees and agreements contained in this Guarantee Agreement
shall bind the successors, assigns, receivers, trustees and representatives of
the Guarantor and shall inure to the benefit of the Holders of the Preferred
Securities then outstanding. Except in connection with a consolidation, merger
or sale involving the Guarantor that is permitted under Article XII of the
Indenture and pursuant to which the assignee agrees in writing to perform the
Guarantor's obligations hereunder, the Guarantor shall not assign its
obligations hereunder, and any purported assignment that is not in accordance
with these provisions shall be void.

Section 8.2.      Amendments.

         Except with respect to any changes that do not materially adversely
affect the rights of the Holders (in which case no consent of the Holders will
be required), this Guarantee Agreement may only be amended with the prior
approval of the Holders of not less than a Majority in Liquidation Amount of the
Preferred Securities. The provisions of Article VI of the Trust Agreement
concerning meetings of the Holders shall apply to the giving of such approval.


                                       15
<PAGE>

Section 8.3.      Notices.

         Any notice, request or other communication required or permitted to be
given hereunder shall be in writing, duly signed by the party giving such
notice, and delivered, telecopied (confirmed by delivery of the original) or
mailed by first class mail as follows:

         (a)      if given to the Guarantor, to the address or telecopy number
set forth below or such other address or telecopy number or to the attention of
such other Person as the Guarantor may give notice to the Holders:

                           F.N.B. Corporation
                           2150 Goodlette Road North
                           Naples, Florida  34102
                           Facsimile No.: (724) 983-3515
                           Attention: Chief Financial Officer

         (b)      if given to the Issuer Trust, in care of the Guarantee
Trustee, at the Issuer Trust's (and the Guarantee Trustee's) address set forth
below or such other address or telecopy number or to the attention of such other
Person as the Guarantee Trustee on behalf of the Issuer Trust may give notice to
the Holders:

                           FNB Capital Trust I
                           c/o F.N.B. Corporation
                           2150 Goodlette Road North
                           Naples, Florida  34102
                           Facsimile No.:  (724) 983-3515
                           Attention:  Chief Financial Officer

                           with a copy to:
                           Wilmington Trust Company
                           Rodney Square North
                           1100 North Market Street
                           Wilmington, Delaware  19890-0001
                           Attention: Corporate Trust Administration

         (c)      if given to the Guarantee Trustee:

                           Wilmington Trust Company
                           Rodney Square North
                           1100 North Market Street
                           Wilmington, Delaware  19890-0001
                           Attention: Corporate Trust Administration

         (d)      if given to any Holder, at the address set forth on the books
and records of the Issuer Trust.


                                       16
<PAGE>

         All notices hereunder shall be deemed to have been given when received
in person, telecopied with receipt confirmed, or mailed by first class mail,
postage prepaid, except that if a notice or other document is refused delivery
or cannot be delivered because of a changed address of which no notice was
given, such notice or other document shall be deemed to have been delivered on
the date of such refusal or inability to deliver.

Section 8.4.      Benefit.

         This Guarantee Agreement is solely for the benefit of the Holders and
is not separately transferable from the Preferred Securities.

Section 8.5.      Interpretation.

         In this Guarantee Agreement, unless the context otherwise requires:

         (a)      capitalized terms used in this Guarantee Agreement but not
defined in the preamble hereto have the respective meanings assigned to them in
Section 1.1;

         (b)      a term defined anywhere in this Guarantee Agreement has the
same meaning throughout;

         (c)      all references to "the Guarantee Agreement" or "this Guarantee
Agreement" are to this Guarantee Agreement as modified, supplemented or amended
from time to time;

         (d)      all references in this Guarantee Agreement to Articles and
Sections are to Articles and Sections of this Guarantee Agreement unless
otherwise specified;

         (e)      a term defined in the Trust Indenture Act has the same meaning
when used in this Guarantee Agreement unless otherwise defined in this Guarantee
Agreement or unless the context otherwise requires;

         (f)      a reference to the singular includes the plural and vice
versa; and

         (g)      the masculine, feminine or neuter genders used herein shall
include the masculine, feminine and neuter genders.

Section 8.6.      Governing Law.

         THIS GUARANTEE AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED AND
INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD
TO THE CONFLICT OF LAW PRINCIPLES THEREOF.


                                       17
<PAGE>

Section 8.7.      Counterparts.

         This instrument may be executed in any number of counterparts, each of
which so executed shall be deemed to be an original, but all such counterparts
shall together constitute but one and the same instrument.

                    [SIGNATURES APPEAR ON THE FOLLOWING PAGE]


                                       18
<PAGE>

         THIS GUARANTEE AGREEMENT is executed as of the day and year first above
written.

                                    F.N.B. CORPORATION
                                    as Guarantor



                                    By:
                                       ---------------------------------
                                    Name:
                                    Title:


                                    WILMINGTON TRUST COMPANY,
                                    as Guarantee Trustee
                                      and not in its individual capacity



                                    By:
                                       ---------------------------------
                                    Name:
                                    Title:


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