Equilibrium geometries, harmonic vibrational frequencies, and dissociation energies were determined for PbS, PbS-, PbO and PbO-molecules by density functional methods (B3LYP, B3PW91, BLYP and BHLYP), molecular orbital method (MP2) and quadratic Cl calculation by including single and double substitutions (QCISD). The calculated results indicate that all methods used in this study have good performance in predicting the geometries, and in most cases harmonic vibrational frequencies. For dissociation energy, BHLYP gives the best agreement with experiments and previous theoretical studies on PbO, compared with other methods used in this study. (C) 2003 Elsevier Science B.V. All rights reserved.