Exhibit 99.1

                             FIRST FINANCIAL BANCORP
              CERTIFICATION OF CHIEF EXECUTIVE OFFICER 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 Annual Report of First  Financial  Bancorp (the
"Company")  on Form 10-K for the period ended  December 31, 2002,  as filed with
the Securities  and Exchange  Commission on the date hereof (the  "Report"),  I,
Leon  Zimmerman,  President and Chief Executive  Officer of the Company,  hereby
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; and

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

/s/  Leon Zimmerman
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Leon Zimmerman
Chief Executive Officer
March 21, 2003

A signed  original of this  written  statement  required by Section 906 has been
provided to First  Financial  Bancorp  and will be  retained by First  Financial
Bancorp and  furnished to the  Securities  and Exchange  Commission or its staff
upon request.