The mechanism of N2O decomposition on the platinum and copper loaded carbon film catalysts was studied using in situ FTIR spectroscopy at the temperature range 200-600 degrees C. It was experimentally proved that on these catalysts, carbon becomes not only a support but also a reactant due to the formation of the surface oxygen complexes. The oxidation and dissociation of surface oxides play a significant role in the overall process due to the formation of the new active centres. It is experimentally proved that -NCO formation is a major step in the overall mechanism at the low temperature range.