The selective reduction of NO over Cu-, Co- and H-mordenite was studied using CH4, C2H4 and CH3OH, and compared with the same reaction in the gas phase. Co- and H-mordenite proved to be active and selective for the three reducing agents, while Cu-mordenite was so only when C2H4 and CH3OH were used. Besides being reduced in the presence of O-2, NO acted as a homogeneous catalyst in the oxidation of CH4 and C2H4. A free-radical mechanism similar to the one occuring in the methane partial oxidation reaction could explain that behavior. Interestingly, on Co-mordenite, the conversion of nitric oxide to nitrogen began to occur at similar temperatures for both CH4 and CH3OH. For both Co-M and Cu-M the NO to N-2 conversion started after the CH3OH conversion reached 100%. In the gas-phase reaction no NO conversion was observed when CH4 or C2H4 were used as reducing agents, but a 30% of the nitric oxide conversion was obtained when CH3OH was the reducing reactant at 600 degrees C, Very similar results were observed with or without O, in the feed stream. When catalysts were present, the presence of oxygen noticeably increased the rate of NO to N-2 conversion.