The adsorption of NO on the oxygen site of several metal oxide surfaces is discussed. It is shown that the strength of the interaction and the variation of the bond lengths are not always correlated to the electron transfer from NO to the surface atoms. In cases of irreducible metal oxides, NO22- may be strongly adsorbed. The formation of NO2- on reducible metal oxide is difficult unless terminal oxygen is present on the surface. Then, the reduction of the surface by transferring the unpaired electron from the NO to the surface appears in DFT calculations (VASP code). (c) 2005 Elsevier B.V. All rights reserved.