The catalytic reduction of dinitrogen monoxide (N2O) by ethylene (C2H4) in the absence and presence Of O-2 is studied over Fe-ZSM-5 catalysts. Two types of carbonaceous deposits (Calpha, Cbeta) are formed on Fe-ZSM-5 during the reduction of N2O by C2H4 in the absence Of O-2. The catalytic activity of Fe-ZSM-5 decreases with an increase in the amount of Calpha, while the catalytic activity is not affected by the presence of Cbeta. The formation of these carbonaceous deposits is suppressed by the presence Of O-2 in the feed gas, and the catalytic reduction of N2O by C2H4 is promoted by O-2, since deactivation of Fe sites is prevented in the presence of O-2. (C) 2003 Elsevier Inc. All rights reserved.