We compare the electronic properties of Cu(111) and Cu(2)O(111) surfaces in relation to the dissociation of NO using first principles calculations within density functional theory. We note a well-defined three-fold site on both O- and Cu-terminated Cu(2)O surfaces which is verified as the active site for the adsorption and dissociation of NO. The interaction of Cu with O atoms results in the forward shifting of the local density of states and formation of unoccupied states above the Fermi level, compared to the fully occupied d band of pure Cu. These results give valuable insights in the realization of a catalyst without precious metal for the dissociation of NO.