Results of quantum density functional theory (B3LYP) calculations on the decomposition of NO to N2O in the presence of Cu are reported. Three approaches of NO interacting with Cu and two decomposition channels via cis- and trans-(NO)2 dimers have been identified. The configuration of NO approaching to the Cu atom with N is more stable than the other two configurations, in which the NO interacts with Cu via oxygen. At low temperature, NO is in favor of decomposing to N2O via the trans-intermediate Min6 in the presence of Cu atom, because the decomposition activation energy of this channel is only 61.1 kJ/mol at the B3LYP/Lanl2DZ level, and lower than the other decomposition channel''s. The potential energy surface shows that the cis-intermediate Min8 is highly stabilized both thermodynamically and kinetically at low temperature, and the calculation results also suggest that the N–O bond is more easily dissociated than the Cu–O bond in the Min8. Hence, it is very different for the NO decomposition between in the gas phase and in the presence of Cu. [Copyright &y& Elsevier]