The catalytic reduction of dinitrogen monoxide (N2O) by various hydrocarbons (CH4, C2H4, C1H6, C3H6, C3H8) in the absence and presence of 0, has been studied over Fe-ZSM-5 catalysts. These hydrocarbon reductants are phenomenologically divided into three groups, namely CH4, C3H6, and others (C2H4, C2H6, C3H8), referred to as the CH4 group. Two types of carbonaceous deposits (Calpha, Cbeta) are formed on Fe-ZSM-5 during the reduction of N2O by C-2 and C-3 hydrocarbons in the absence of O-2. In both cases of C2H4 and C3H6, the catalytic activity of Fe-ZSM-5 decreases with an increase in the amount of Calpha, while it is not affected by the presence of Cbeta. The Calpha species is formed on Fe sites and the Cbeta is mainly accumulated on the support. The formation of these carbonaceous deposits from the C2H4 group is suppressed by the presence of O-2 in the feed gas, and this promotes the catalytic reduction of N2O. The amount and the chemical nature of Calpha formed in the cases of the C2H4 group and C3H6 are similar, while those of Cbeta are significantly different. The reactivity of Cbeta with O-2 should be different and this may be responsible for the difference in the effects of O-2 addition on the reduction of N2O between the C2H4 group and C3H6. In the case of CH4. a high stable conversion of NO is obtained irrespective of the presence and absence of O-2 because the carbonaceous deposits are scarcely accumulated on the catalyst. (C) 2004 Elsevier B.V. All rights reserved.