By using the density functional theory (DFT), we calculated some properties such as the energies of highest occupied molecular orbital (HOMO) orbitals and the atomic charges which are related to the reactive behavior of 2-mercaptobenzoxazole (MBO) and its methyl and methoxy derivatives. The results of the calculations indicated that the efficiencies of MBO and its derivatives depend on the investigated parameters, and 2-mercaptobenzothiazole (MBT) is better than MBO as a collector agent. Electron donating groups at the 6-position of MBO provided the best efficiency for MBO molecule. The introduction of the methyl group to any position of the benzene ring makes also MBO more powerful chelating agent by increasing the atomic charges on the N and S atoms. The theoretically obtained results are consistent with the experimental data reported in the literature. (c) 2006 Elsevier B.V. All rights reserved.