Two SiO₂ supported Ag catalysts with 5 wt% Ag in each were prepared by impregnation and radiolysis methods. These catalysts were characterized by BET surface area, temperature programmed reduction (TPR) and X-ray diffraction techniques. TPR results indicate the presence of metallic silver in the catalyst prepared by radiolysis method whereas Ag⁺ precursor is formed in the catalyst prepared by impregnation method. The Ag particle size as calculated from the XRD patterns, in the catalyst prepared by radiolysis method is relatively smaller compared to that of the impregnated catalyst. The two catalysts are tested for decomposition of N₂O and it is observed that the catalyst prepared by radiolysis gives higher conversion and better N₂ selectivity. These results suggest that radiolysis method yields metallic Ag nanoparticles directly without any reduction treatment and that the catalyst exhibits good activity in N₂O decomposition.