LaCoO3, Co3O4 and a mix of them, prepared by two different methods, were studied for the CO+NO reaction under two different gas mixtures. Under the binary gas mixture, we have shown two types of reduction reaction of NO : at low temperature, N2O is formed, and at high temperature N-2 is formed. On Co3O4, we have observed the decomposition of N2O in the medium temperature range. Under the complete gas mixture, no NO decomposition was observed whatever the catalyst. But for the perovskite LaCoO3 obtained from simultaneous precipitation, containing 4.5% of potassium, we have pointed out an adsorption/desorption phenomenon, which can be very interesting in the application of NO storage.