The activity of ZSM-5 and boralite zeolites (Na, H and Cu forms) in the reduction of nitric oxide with propane/oxygen is compared. Copper ion-exchanged boralite is more active than a corresponding Cu-ZSM-5 sample with the same MFI structure, Si/M (M = Al or B) ratio and copper content, showing that in copper-exchanged samples Bronsted acid sites do not play a key role in the reaction mechanism, in contrast to that found for samples without the exchanged transition metal.