The interaction of molecular oxygen with the Cu(1 0 0) surface has been studied by using both Hartree–Fock and density functional methods in the framework of the cluster model approach. In this study, we have used the Cu8(6,2) cluster in order to simulate the O2 molecular adsorption on different high symmetry chemisorption sites (top–top, bridge–fourfold, bridge–top, fourfold–fourfold) on the Cu(1 0 0) surface. High level non-local density functional (NLSD) computations indicate that the more stable chemisorption site is the bridge–bridge followed by the top–top, bridge–top and bridge–fourfold ones. The calculated 1s O XPS shifts are in good agreement with the experimental indications.