The influence of the oxide support (i.e., Al2O3, Nb2O5, SiO2, and TiO2) on the surface properties, reduction and oxidation properties, acid-base properties, and catalytic activity of supported indium oxide catalysts has been investigated by temperature-programmed reduction/oxidation, thermogravimetry coupled to differential scanning calorimetry, ammonia and sulfur dioxide adsorption calorimetry, and reduction of NO, by ethene in highly oxygen-rich atmosphere. Two series of In2O3-containing catalysts at low (approximate to 3 wt %) and at theoretical geometric monolayer (from 20 to 40 wt %) In2O3 Content were prepared and their properties were compared with unsupported In2O3 material. Supports able to disperse the In2O3 aggregates with high In stabilization gave rise to active catalytic systems. Among the studied oxide supports, Al2O3 and, to a lower extent, TiO2 were found to be the best supports for obtaining active de-NO, catalysts.