Co3O4 oxide catalysts prepared on different commercial supports, namely, TiO2, Al2O3, and Mg-Al mixed oxides with various Mg and Al concentrations, were characterized by atomic absorption spectrometry, Brunauer-Emmett-Teller method, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and H-2 temperature-programmed reduction, tested for N2O decomposition, and compared with bulk Co3O4. In spite of the fact that Co3O4/70Mg30Al also contained hardly reducible compounds, it possessed the highest catalytic activity, probably due to the presence of active sites with easier reducibility and better dispersion of the active phase on the support contributing to a higher number of active sites. The conversion over Co3O4-supported tablets is comparable with that of the same catalyst bed of bulk Co3O4 tableted catalyst.