EXHIBIT 99.3


                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Financial Institutions, Inc. (the
"Company") on Form 10-Q for the quarterly period ended June 30, 2002, as filed
with the Securities and Exchange Commission on August 12, 2002 (the "Report"),
I, Ronald A. Miller, Senior Vice President and Chief Financial Officer of the
Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to
Section 906 of the Sarbanes-Oxley Act of 2002, that:

1. The Report fully complies with the requirements of Section 13(a) or 15(d) of
the Securities Exchange Act of 1934, as amended; and

2. The information contained in the Report fairly presents, in all material
respects, the financial condition and results of operations of the Company.

By: /s/ Ronald A. Miller
   -----------------------------
      Ronald A. Miller
      Senior Vice President and
      Chief Financial Officer
      August 12, 2002