The room temperature decomposition of N2O over prereduced Rh-based catalysts (Rh supported on ceria, zirconia and titania-alumina) is studied as a function of the oxygen content in the feed. Results indicate that Rh supported on titania-alumina shows lower degree of inhibition by gaseous oxygen on this reaction, attributed to the role of the metal particle-support interface region in the reaction. The effect of Rh loading and of the reaction temperature are consistent with the hypothesis.