In this study, we present the adsorption behavior of NO, NO2 and H2O on trivalent rare-earth ion-exchanged ZSM-5 (REZSM-5; RE = La, Ce. Nd, Sm, Gd and Dy) using density functional theory. The results show that Ce-ZSM-5 is more effective for the activation of NOx than La-ZSM-5 and Nd-ZSM-5, which is in good agreement with experimental results. The present investigation also suggests that Dy-ZSM-5 has a considerable ability for the activation of NO2 as compared to Sm-ZSM-5 and Gd-ZSM-5. Furthermore, the Ce-, Nd- and Dy-analogues posses a quite stronger affinity for NO,, and that the low affinity of H2O indicate the poisoning resistance ability of these catalysts. In addition, the relationship between the adsorption energy of NO and the contribution of NO-2pi(g)(1) molecular orbital was also investigated in the NO/RE-ZSM-5 adsorption complex. (C) 2002 Elsevier Science B.V All rights reserved.