The selective catalytic reduction (SCR) process of NO in the presence of modified zeolite catalysts has been studied. Low molecular weight hydrocarbons (methane and ethene) were used as reducing agents. The catalytic performance of Cu-containing ZSM-5, mordenite and ferrierite was exemplified using ethene. The effect of Cu content was shown for ferrierite matrix and related to the performance of its pure hydrogen form. A comparison of the catalytic properties of Cu-MFI and Co-FER was carried out for methane and ethene. A series of doubly substituted In,Co-FER catalysts with different metal loading (0.25-0.75Co and 0.6-1.2In) were studied using methane. The cobalt and indium ions, when present simultaneously in ferrierite, exert a pronounced synergetic effect in the title reaction in the presence of methane. This effect was evidenced in the broad range of the In-Co loading. Finally, the question of how the zeolite matrix does affect the SCR process with methane, when using the In,Co-forms, was addressed for ferrierite and ZSM-5 type zeolites. (c) 2005 Elsevier B.V. All rights reserved.