In this work, Pd/NaY-zeolite and Pd-W/NaY-zeolite catalysts were prepared from the compounds Pd(NO3)(2) and [W(CO)(6)]. Palladium catalysts supported on NaY-zeolite were prepared by ion exchange and impregnation methods. Subsequently, tungsten was added by photochemical activation Of [W(CO)61 in order to obtain a Pd-W interaction. The catalysis materials were characterized by diffuse reflectance (DRIFTS)-FTIR, chemical analysis (AAS), temperature programmed reduction (TPR), X-ray diffraction (XRD), H-2 chernisorption and sorption measurements. The prepared catalysts were found to be active for NO decomposition at 573 K leading mainly to N-2 and N2O. The conversion of NO and the selectivity to N2O were studied as a function of time and the reduction temperature. The Pd/NaY-zeolite and the Pd-W/NaY-zeolite samples exhibited an initial period of high and constant activity followed by deactivation. For samples reduced at 573 K the deactivation process becomes more pronounced in the presence of tungsten. On the other hand when the reduction pretreatment was carried out at 973 K the presence of tungsten allowed the catalysts to have a higher conversion for a longer period of time. Tungsten prevents the sintering of small palladium particles. Another beneficial effect of tungsten was a significant suppression of N2O formation. The selectivity for N2O at similar NO conversion level was lower on Pd-W/NaY-zeolite. (C) 2003 Elsevier B.V. All rights reserved.