CDW 10-Q 2005 Q2 Quarterly report

Exhibit 32.2

Certification Pursuant to Section 1350 of Chapter 63
of Title 18 of the United States Code

     I, Barbara A. Klein, the chief financial officer of CDW Corporation (“CDW”), certify that (i) the Quarterly Report of Form 10-Q for the three months ended June 30, 2005 (the “10-Q”) of CDW fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and (ii) the information contained in the 10-Q fairly presents, in all material respects, the financial condition and results of operations of CDW.

  /s/ Barbara A. Klein  

  Barbara A. Klein 

  Senior Vice President and Chief Financial Officer
  CDW Corporation
  August 8, 2005