<PAGE>

                                                                    EXHIBIT 10.9

                                 PROMISSORY NOTE

U.S. $275,000                                                  October 1st, 2004

After the payment effected on June 30 2004 and September 30 2004, related to the
following promissory notes:

<TABLE>
<S>                  <C>
January 2nd, 2003    $   359,788
February 3rd, 2003   $     8,595
March 3rd, 2003      $  2,313.50
April 1st, 2003      $   107,187
May 1st, 2003        $    21,683
June 2nd, 2003       $  2,231.98
July 29th, 2003      $   600,000
October 20, 2003     $   500,000
December 31st, 2003  $291,180.76
February 24th, 2004  $   500,000
</TABLE>

the total outstanding principal on the listed promissory notes is $ 275,000.
This document summarizes the listed promissory notes within a single residual
one:

FOR VALUE RECEIVED, CYNOSURE, INC., a corporation organized under the laws of
Delaware ("Borrower"), 10 Elizabeth Drive, Chelmsfoid, MA 01824, agrees to pay
to El En SpA (Lender"), Via Baldanzese 17, 50041 Calenzano, Firenze, Italy, or
order, the principal sum of Two Hundred Seventy Five Thousand U.S. Dollars
($275,000), on demand, together with interest from the date hereof on the unpaid
principal balance at the rate specified below, until repaid in full. Prepayment
of principal, together with accrued interest, may be made at any time without
penalty. Interest hereon shall accrue from the date hereof at the rate of five
(5%) percent per annum. All accrued and unpaid interest and the unpaid principal
amount of this Note shall be due and payable upon the earlier of (a) written
demand for payment delivered by Lender to Borrower, or (b) the consummation of
any Financing by Borrower, as such term is defined below (the "Maturity Date").
For purposes of this Note, the term "Financing" shall mean any equity or debt
financing or financings consummated by Borrower after the date of this Note in
which the Borrower raises a cumulative total of $10,000,000.

In the event that any amount of principal hereof, or (to the extent permitted by
applicable law) any interest hereon or any other amount payable hereunder is not
paid in full when due (whether at stated maturity, by acceleration or
otherwise), Borrower shall pay interest (after as well as before entry of
judgment thereon to the extent permitted by law) on such unpaid amount to
Lender, from the date such amount becomes due until the date such amount is paid
in full, payable on demand of Lender at a rate per annum equal at all times to
12% per annum (the "Default Rate"). Additionally, and without limiting the
foregoing, following the occurrence and during the continuance of any Event of
Default (as defined below), at the option of Lender, the interest rate shall be
the Default Rate. Such interest on overdue amounts shall be payable on demand.
All computations of interest shall be made on the basis of a year of 360 days
for the actual number of days (including the first day but excluding the last
day) occurring in the period for which such interest is payable. Each
determination by Lender of any applicable rate of interest, and of any change
therein, in the absence of manifest error shall be conclusive and binding on the
parties hereto.

Payment shall be made in lawful tender of the United States unconditionally in
full without set-off, counterclaim or, to the extent permitted by applicable
law, other defense, all of which rights of Borrower are hereby expressly waived
by Borrower. All payments hereunder shall be made to Lender at his address set
forth above (or to such other place as Lender shall designate in a written
notice to Borrower), and, unless Borrower has obtained Lender's written consent
to another form of payment, such payment shall be made by wire transfer of
immediately available funds by no later than 12:00 noon (Boston time) on the due
date of the payment, in accordance with Lender's payment instructions.

                                      -1-

<PAGE>

Whenever any payment hereunder shall be stated to be due, or whenever any
interest payment date or any other date specified hereunder would otherwise
occur, on a day other than a Business Day (as defined below), then such payment
shall be made, and such interest payment date or other date shall occur, on the
next succeeding Business Day, and such extension of time shall in such case be
included in the computation of payment of interest hereunder. As used herein,
"Business Day" means a day (i) other than Saturday or Sunday, and (ii) on which
commercial banks are open for business in Boston, Massachusetts.

Borrower represents and warrants to Lender that:

      (i) Organization and Powers. Borrower is a corporation duly organized,
validly existing and in good standing under the laws of the State of Delaware,
and has all requisite power and authority to own its assets and carry on its
business and to execute, deliver and perform its obligations under this Note.

      (ii) Authorization; No Conflict. The execution, delivery and performance
by Borrower of this Note have been duly authorized by all necessary corporate
action of Borrower and do not and will not (A) contravene the terms of the
constitutional documents of Borrower; or (B) result in a breach of or constitute
a default under any material lease, instrument, contract or other agreement to
which Borrower is a party or by which it or its properties may be bound or
affected; or (C) violate any provision of any law, rule, regulation, order,
judgment, decree or the like binding on or affecting Borrower.

      (iii) Binding Obligations. This Note constitutes the legal, valid and
binding obligation of Borrower, enforceable against Borrower in accordance with
its terms.

      (iv) Consents. No authorization, consent, approval, license, exemption of,
or filing or registration with, any governmental authority or agency, or
approval or consent of any other person or entity is required for the due
execution, delivery or performance by Borrower of this Note.

Any of the following events which shall occur shall constitute an "Event of
Default":

      (a) Payments. Borrower shall fail to pay when due any amount of principal
hereof, or interest hereon or other amount payable hereunder, and such failure
shall continue unremedied for five (5) days.

      (b) Representations and Warranties. Any representation or warranty by
Borrower under or in connection with this Note shall prove to have been
incorrect in any material respect when made or deemed made.

      (c) Insolvency, (i) Borrower shall (A) admit in writing its inability to,
or shall fail generally or be generally unable to, pay its debts (including its
payrolls) as such debts become due, (B) make a general assignment for the
benefit of creditors, (C) be dissolved, liquidated, wound up or cease its
corporate existence, or (D) commence any voluntary proceeding or case seeking to
adjudicate it a bankrupt or insolvent, or seeking reorganization, arrangement,
adjustment, intervention, suspension of payments, or composition of it or its
debt under any law relating to bankruptcy, insolvency, suspension of payments or
reorganization or relief of debtors, or seeking appointment of a receiver,
trustee, intervenor or liquidator, or other similar official for it or for any
substantial part of its property, (ii) an involuntary proceeding or case shall
be commenced against Borrower seeking any of the foregoing relief and remain
undismissed for a period of 30 days; (iii) an order for relief or other order or
adjudication shall be entered against Borrower under any such bankruptcy,
insolvency or similar law; (iv) any receiver, trustee, or other official or
Person shall be appointed to take possession of any property of Borrower; or (v)
Borrower shall take any corporate action to authorize, or shall consent to, any
of the actions or events set forth above in this paragraph.

If any Event of Default shall occur and be continuing, Lender may, by notice to
Borrower, declare the entire unpaid principal amount of this Note, all interest
accrued and unpaid hereon and all other amounts due hereunder to be forthwith
due and payable, whereupon the principal hereof, all such accrued interest and
all such other amounts shall become and be forthwith due and payable, without
presentment, demand, protest or further notice of any kind, all of which are
hereby expressly waived by Borrower, provided that if an event described in
paragraph (c) above shall

                                     -2-

<PAGE>

occur, the result which would otherwise occur only upon giving of notice by
Lender to Borrower as specified above shall occur automatically, without the
giving of any such notice.

Borrower agrees to pay on demand the costs and expenses of Lender, and fees and
disbursements of Lender's counsel, in connection with any Event of Default, the
enforcement or attempted enforcement of, and preservation of any rights or
interests under, this Note, and any out-of-court workout or other refinancing or
restructuring or any bankruptcy or insolvency case or proceeding.

No single or partial exercise of any power under this Note shall preclude any
other or further exercise of such power or exercise of any other power. No delay
or omission on the part of Lender in exercising any right under this Note shall
operate as a waiver of such right or any other right thereunder.

All notices and other communications provided for hereunder shall, unless
otherwise stated herein, be in writing and mailed, sent or delivered to the
respective parties hereto at or to their respective addresses set forth herein,
or at or to such other address as shall be designated by any party in a written
notice to the other party hereto. All such notices and communications shall be
effective (i) if delivered by hand, when delivered; (ii) if sent by overnight
courier service, when delivered; and (iii) if sent by mail, upon the earlier of
the date of receipt or five Business Days after deposit in the mail, first class
(or air mail, with respect to communications to be sent to or from the United
States), postage prepaid.

This Note shall be binding on Borrower and its successors and assigns, and shall
be binding upon and inure to the benefit of Lender, any future holder of this
Note and their respective successors and assigns. Borrower may not assign or
transfer this Note or any of its obligations hereunder without Lender's prior
written consent.

This Note shall be governed by and construed in accordance with the laws of the
Commonwealth of Massachusetts.

Borrower hereby (a) submits to the non-exclusive jurisdiction of the courts of
the Commonwealth of Massachusetts and the Federal courts of the United States
sitting in the District of Massachusetts (collectively, the "Massachusetts
Courts"), for the purpose of any action or proceeding arising out of or relating
to this Note, (b) irrevocably waives (to the extent permitted by applicable law)
any objection which it now or hereafter may have to the laying of venue of any
such action or proceeding brought in any of the Massachusetts Courts, and any
objection on the ground that any such action or proceeding in any Massachusetts
Court has been brought in an inconvenient forum, and (c) agrees that (to the
extent permitted by applicable law) a final judgment in any such action or
proceeding brought in a Massachusetts Court shall be conclusive and may be
enforced in other jurisdictions by suit on the judgment or in any other manner
permitted by law.

IN WITNESS WHEREOF, Borrower signing below by its duly authorized legal
representative(s) has executed this Note as of the date first above mentioned.

                                 Cynosure Inc.,

                                 By: /s/ Michael Davin
                                     ---------------------------------
                                 Name: Michael Davin
                                 Title: Chief Executive Officer

                                      -3-