The decomposition of nitrogen oxide has been studied under non steady state reaction conditions over a La-stabilised Cu-ZSM5 structured catalyst after adsorbing NO on the zeolite. The three main steps of the experiments are the following: (i) NO adsorption at 50 degrees C until zeolite saturation, (ii) reactor isolation and heating up to the reaction temperature (480 or 520 degrees C), (iii) cooling down back to 50 degrees C re-opening the reactor once the adsorption temperature has been reached. No NO are emitted during all steps. TPD tests have been performed after one or more cycles (i)-(iii) to check the mass balance. A very high NO conversion, much higher than those obtained under flowing (steady state) reaction conditions, is reached in all cycles. The unreacted NO is readsorbed on the zeolite in the step (iii). After two/three cycles (steps i-iii) the experiments a re repeatable. The effect of O-2 (2.5 vol.%) co-feeding during adsorption step has been also studied; the adsorption capacity during the first cycle is higher than that obtained under O-2-free reaction conditions, while NO conversion decreased. After few cycles, adsorption capacity and NO conversion appeared unaffected by O-2 feed. (C) 2013 Elsevier B.V. All rights reserved.