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                                                                     EXHIBIT 4.3

              CERTIFICATE OF TRUST OF MB FINANCIAL CAPITAL TRUST I

     THIS Certificate of Trust of MB Financial Capital Trust I (the "Trust") is
being duly executed and filed by Wilmington Trust Company, a Delaware banking
corporation, as trustee, to form a business trust under the Delaware Business
Trust Act (12 DEL. C. Section 3801 ET SEQ.)(the "Act").

     1.   NAME. The name of the business trust formed hereby is MB Financial
Capital Trust I.

     2.   DELAWARE TRUSTEE. The name and business address of the trustee of the
Trust in the State of Delaware is Wilmington Trust Company, 1100 North Market
Street, Wilmington, Delaware 19890-0001, Attention Corporate Trust
Administration.

     3.   EFFECTIVE DATE. This Certificate of Trust shall be effective upon
filing.

     IN WITNESS WHEREOF, the undersigned has executed this Certificate in
accordance with Section 3811(a) of the Act.

                                            WILMINGTON TRUST COMPANY

                                            By: /s/ James P. Lawler
                                                -------------------
                                            Name:   James P. Lawler
                                            Title:  Vice President<Page>

                                                                     EXHIBIT 4.4

                                 TRUST AGREEMENT

     This TRUST AGREEMENT, dated as of July 22, 2002 (this "Trust Agreement"),
between (i) MB FINANCIAL, INC., a Maryland corporation (the "Depositor"), and
(ii) WILMINGTON TRUST COMPANY, a Delaware banking corporation, as trustee
(together with any other trustees of the Trust, the "Trustees"). The Depositor
and the Trustees hereby agree as follows:

          1.   The trust created hereby (the "Trust") shall be known as "MB
Financial Capital Trust I" in which name the Trustees, or the Depositor to the
extent provided herein, may engage in the transactions contemplated hereby, make
and execute contracts, and sue and be sued.

          2.   The Depositor hereby assigns, transfers, conveys and sets over to
the Trustees the sum of $500.00. The Trustees hereby acknowledge receipt of such
amount in trust from the Depositor, which amount shall constitute the initial
trust estate. The Trustees hereby declare that they will hold the trust estate
in trust for the Depositor. It is the intention of the parties hereto that the
Trust created hereby constitute a statutory business trust under Chapter 38 of
Title 12 of the Delaware Code, 12 DEL. C. Section 3801, ET SEQ. (the "Trust
Act"), and that this document constitutes the governing instrument of the Trust.
The Trustees are hereby authorized and directed to execute and file a
certificate of trust in the form of exhibit A attached hereto with the Delaware
Secretary of State in accordance with the provisions of the Trust Act.

          3.   The Depositor and the Trustees will enter into an amended and
restated Trust Agreement, satisfactory to each such party and substantially in
the form included as an exhibit to the 1933 Act Registration Statement (as
defined below), to provide for the contemplated operation of the Trust created
hereby and the issuance of the preferred securities and common securities
referred to therein (collectively, the "Trust Securities"). Prior to the
execution and delivery of such amended and restated Trust Agreement, the
Trustees shall not have any duty or obligation hereunder or with respect to the
trust estate, except as otherwise required by applicable law or as may be
necessary to obtain prior to such execution and delivery of any licenses,
consents or approvals required by applicable law or otherwise.

          4.   The Depositor and the Trustees hereby authorize and direct the
Depositor, as agent of the Trust, (i) to file with the Securities and Exchange
Commission (the "Commission") and execute, in each case on behalf of the Trust,
(a) the Registration Statement on Form S-1 (the "1933 Act Registration
Statement"), including any pre-effective or post-effective amendments to the
1933 Act Registration Statement, relating to the registration under the
Securities Act of 1933, as amended, of the preferred securities of the Trust and
(b) a Registration Statement on Form 8-A (the "1934 Act Registration Statement")
(including all pre-effective and post-effective amendments thereto) relating to
the registration of the preferred securities of the Trust under the Securities
Exchange Act of 1934, as amended; (ii) to file with the New York Stock Exchange
or any other national stock exchange or The Nasdaq National Market (each, an
"Exchange") and execute on behalf of the Trust one or more listing applications
and all other applications, statements, certificates, agreements and other
instruments as shall be necessary or desirable to cause the preferred securities
to be listed on any of the Exchanges; (iii)

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to file and execute on behalf of the Trust such applications, reports, surety
bonds, irrevocable consents, appointments of attorney for service of process and
other papers and documents as shall be necessary or desirable to register the
preferred securities under the securities or blue sky laws of such jurisdictions
as the Depositor, on behalf of the Trust, may deem necessary or desirable, (iv)
to execute and deliver letters or documents to, or instruments for filing with,
a depository relating to the preferred securities of the Trust, and (v) to
execute on behalf of the Trust that certain underwriting agreement relating to
the preferred securities, among the Trust, the Depositor and the several
underwriters named therein, substantially in the form included as an exhibit to
the 1933 Act Registration Statement.

          5.   The number of Trustees initially shall be one (1) and thereafter
the number of Trustees shall be such number as shall be fixed from time to time
by a written instrument signed by the Depositor which may increase or decrease
the number of Trustees; provided, however, that to the extent required by the
Trust Act, one Trustee shall either be a natural person who is a resident of the
State of Delaware or, if not a natural person, an entity which has its principal
place of business in the State of Delaware and otherwise meets the requirements
of applicable Delaware law. Subject to the foregoing, the Depositor is entitled
to appoint or remove without cause any Trustee at any time. The Trustees may
resign upon thirty (30) days' prior notice to the Depositor.

          6.   (a) The Trustees and their officers, directors, agents and
servants (collectively, the "Fiduciary Indemnified Persons") shall not be
liable, responsible or accountable in damages or otherwise to the Trust, the
Depositor, the Trustees or any holder of the Trust Securities (the Trust, the
Depositor and any holder of the Trust Securities being a "Covered Person") for
any loss, damage or claim incurred by reason of any act or omission performed or
omitted by the Fiduciary Indemnified Persons in good faith on behalf of the
Trust and in a manner the Fiduciary Indemnified Persons reasonably believed to
be within the scope of authority conferred on the Fiduciary Indemnified Persons
by this Trust Agreement or by law, except that the Fiduciary Indemnified Persons
shall be liable for any such loss, damage or claim incurred by reason of the
Fiduciary Indemnified Person's negligence or willful misconduct with respect to
such acts or omissions.

          (b)  The Fiduciary Indemnified Persons shall be fully protected in
relying in good faith upon the records of the Trust and upon such information,
opinions, reports or statements presented to the Trust by any person as to
matters the Fiduciary Indemnified Persons reasonably believes are within such
other person's professional or expert competence and who has been selected with
reasonable care by or on behalf of the Trust, including information, opinions,
reports or statements as to the value and amount of the assets, liabilities,
profits, losses, or any other facts pertinent to the existence and amount of
assets from which distributions to holders of Trust Securities might properly be
paid.

          (c)  The Depositor agrees, to the fullest extent permitted by
applicable law, (i) to indemnify and hold harmless each Fiduciary Indemnified
Person, or any of its officers, directors, shareholders, employees,
representatives or agents, from and against any loss, damage, liability, tax,
penalty, expense or claim of any kind or nature whatsoever incurred by the
Fiduciary Indemnified Persons by reason of the creation, operation or
termination of the Trust in a manner

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the Fiduciary Indemnified Persons reasonably believed to be within the scope of
authority conferred on the Fiduciary Indemnified Persons by this Trust
Agreement, except that no Fiduciary Indemnified Persons shall be entitled to be
indemnified in respect of any loss, damage or claim incurred by the Fiduciary
Indemnified Persons by reason of negligence or willful misconduct with respect
to such acts or omissions, and (ii) to advance expenses (including legal fees)
incurred by a Fiduciary Indemnified Person in defending any claim, demand,
action, suit or proceeding shall, from time to time, prior to the final
disposition of such claim, demand, action, suit or proceeding, upon receipt by
the Trust of an undertaking by or on behalf of such Fiduciary Indemnified
Persons to repay such amount if it shall be determined that such Fiduciary
Indemnified Person is not entitled to be indemnified as authorized in the
preceding subsection.

          (d)  The provisions of this Section shall survive the termination of
this Trust Agreement or the earlier resignation or removal of the Fiduciary
Indemnified Persons.

     7.   This Trust Agreement shall be governed by, and construed in accordance
with, the laws of the State of Delaware (without regard to conflict of laws
principles).

     8.   This Trust Agreement may be executed in one or more counterparts.

     9.   The Trust may terminate without issuing any Trust Securities at the
election of the Depositor. The Trust shall dissolve and this Trust Agreement
shall terminate unless the Trust issues securities within one year after the
date hereof. Upon dissolution, the Trustee shall file a certificate of
cancellation in accordance with the Trust Act and apply the funds deposited with
it pursuant to Section 2 above to reimburse the Trustee for any filing fees or
other expenses in connection therewith. Any remaining funds shall, after payment
of any other expenses of the Trust, be returned to the Depositor.

                            [SIGNATURE PAGE FOLLOWS]

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     IN WITNESS WHEREOF, the parties hereto have caused this Trust Agreement to
be duly executed as of the day and year first above written.

                              MB FINANCIAL, INC., as Depositor

                              By:   /s/ Jill E. York
                                    ----------------------------
                              Name:  Jill E. York
                              Title: Vice President and Chief Financial Officer

                              WILMINGTON TRUST COMPANY, as Trustee

                              By:   /s/ James P. Lawler
                                    ----------------------------
                              Name:  James P. Lawler
                              Title: Vice President

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