Here we report the interaction of an oxygen molecule with small tin clusters (Sn(n), n = 2-6, and 10) using plane wave based pseudo-potential method followed by the LCAO-MO approach. The interaction of oxygen with small Sn clusters undergoes through dissociative adsorption process. The Sn(2) shows the highest binding with oxygen by releasing 7.13 eV energy. The higher stability of the Sn(2)O(2) cluster was further verified by sharp increase in the energy gap between the HOMO and LUMO energy levels and very high ionization potential value. After oxidation of Sn clusters, the O atoms are attached to small number of Sn atoms, which is in line with the previous experiments. (C) 2011 Elsevier B.V. All rights reserved.