The catalytic behavior of beryllia-supported Pd catalyst for the direct decomposition of NO was compared with that of silica supported one. The TOF of NO decomposition was one order of magnitude larger in the case of Pd/BeO. Over Pd/SiO2, the TOF was increased with the increase of the Pd particle size. On the contrary, over Pd/BeO smaller Pd particles exhibited higher TOF for NO decomposition suggesting some strong electronic or structural interaction between Pd and beryllia. TPD spectra of NO(a) over reduced catalysts indicated that NO was adsorbed on Pd/SiO2 more strongly than on Pd/BeO, and dissociation of NO(a) was easier on the former catalyst. FT-IR spectra of adsorbed NO at room temperature followed by the evacuation at elevated temperatures confirmed this. TPD spectra of O-2 desorbed from oxidized surface indicated that adsorption strength of O(a) is one of the most important factors to determine the catalytic activity of NO decomposition over supported Pd catalysts.