<PAGE>

                                                                  EXHIBIT 31 (2)

                            CERTIFICATION PURSUANT TO
             RULE 13A-14(A) OF THE SECURITIES EXCHANGE ACT OF 1934,
                             AS ADOPTED PURSUANT TO
                  SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, John F. Corcoran, certify that:

1.    I have reviewed this quarterly report on Form 10-Q/A of CNA Surety
      Corporation;

2.    Based on my knowledge, this quarterly report does not contain any untrue
      statement of a material fact or omit to state a material fact necessary to
      make the statements made, in light of the circumstances under which such
      statements were made, not misleading with respect to the period covered by
      this quarterly report;

3.    Based on my knowledge, the financial statements, and other financial
      information included in this quarterly report, fairly present in all
      material respects the financial condition, results of operations and cash
      flows of the registrant as of, and for, the periods presented in this
      quarterly report;

4.    The registrant's other certifying officer and I are responsible for
      establishing and maintaining disclosure controls and procedures (as
      defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for the registrant
      and have:

a)    designed such disclosure controls and procedures, or caused such
      disclosure controls and procedures to be designed under our supervision,
      to ensure that material information relating to the registrant, including
      its consolidated subsidiaries, is made known to us by others within those
      entities, particularly during the period in which this quarterly report is
      being prepared;

b)    evaluated the effectiveness of the registrant's disclosure controls and
      procedures and presented in this quarterly report our conclusions about
      the effectiveness of the disclosure controls and procedures, as of the end
      of the period covered by this quarterly report based on such evaluation;
      and

c)    disclosed in this quarterly report any change in the registrant's internal
      control over financial reporting that occurred during the registrant's
      most recent fiscal quarter (the registrant's fourth fiscal quarter in the
      case of an annual report) that has materially affected, or is reasonably
      likely to materially affect, the registrant's internal control over
      financial reporting; and

5.    The registrant's other certifying officer and I have disclosed, based on
      our most recent evaluation of internal control over financial reporting,
      to the registrant's auditors and the audit committee of the registrant's
      board of directors (or persons performing the equivalent functions):

a)    all significant deficiencies and material weaknesses in the design or
      operation of internal control over financial reporting which are
      reasonably likely to adversely affect the registrant's ability to record,
      process, summarize and report financial information; and

b)    any fraud, whether or not material, that involves management or other
      employees who have a significant role in the registrant's internal control
      over financial reporting.

Date: March 12, 2004


/s/ John F. Corcoran
----------------------------------------

John F. Corcoran
Senior Vice President and Chief Financial Officer


                                       2