Exhibit 99.b. 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 Interim Report of CDI Corp. (the "Company") on Form 10-Q for the three-month period ending March 31, 2003 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), the undersigned Chief Financial Officer of the Company hereby certifies, pursuant to 18 U.S.C. ss.1350, as adopted pursuant to ss.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 respect, the financial condition and results of operations of the Company as of and for the periods covered in the Report. By: /s/ Jay G. Stuart ----------------------------------- Jay G. Stuart Executive Vice President and Chief Financial Officer Dated: May 8, 2003 A signed original of this written statement required by Section 906 has been provided to CDI Corp. and will be retained by CDI Corp. and furnished to the Securities and Exchange Commission or its staff upon request.