The infrared spectra for Co and Cd complexes of sulfanilamide are studied by PM3 method. It has been found that the proposed structures for these compounds derived from IR spectra and X-ray powder diffraction patterns are consistent with the IR spectra simulated by PM3 method. The band assignments on the basis of the 3D dynamic image of the vibrations corresponding to significant modes have also given. Coordination effects on vibrational modes of anilino and sulfonamido groups of sulfanilamide are in close agreement with the observed results. (C) 2003 Elsevier Science B.V. All rights reserved.