Decane-SCR-NOx in the presence of water vapor and NO decomposition were investigated over Cu ions exchanged in ZSM-5 zeolites with various Si/Al and Al distribution. The local environment of the Cu ions in cationic sites was characterized by the combination of Si-29 MAS NMR, Vis-NIR spectroscopy of Cu(II) ions, Cu(l) Vis emission spectroscopy and UV-Vis spectroscopy of Co(II) ions as probes for the presence of Al pairs in the framework. The Cu(II) ions coordinated to four framework oxygens of the alpha- or beta-type cationic sites containing AlO-(Si-O)(2)-Al sequences represent the most active sites in decane-SCR-NOx. On contrary, the Cu(l) ions coordinated to two or three framework oxygens and located at the channel intersection adjacent to the single At atoms in the alpha- or beta-site control predominantly reaction of NO decomposition. (c) 2006 Elsevier B.V. All rights reserved.