This study deals with the catalytic decomposition of N2O over noble metal based catalysts. The deposition of palladium on reducible supports such as LaCoO3 leads to higher activity from temperature-programmed experiments in comparison with conventional supports such as alumina. Such a different catalytic behaviour cannot be completely explained by changes in the metal dispersion but also by the extent of the metal/support interaction. Interestingly, successive reductive (250 degrees C in H-2) and oxidative thermal treatments in the reactant mixture at high temperature enhance the conversion of N2O particularly on perovskite support. Additional surface characterisations show a re-dispersion and the stabilisation of palladium species in unusual oxidation states which would originate a rate enhancement in the decomposition of N2O. (C) 2007 Elsevier Inc. All rights reserved.