The influence of modifying additives of Ce, Zr, La and Cs oxides on the electronic state of palladium supported on gamma-Al2O3 has been studied by IR-spectroscopy of adsorbed CO, diffuse reflectance UV-visible spectroscopy, X-ray diffraction (XRD) and H-2 chemisorption. The modified supports have been prepared using impregnation, coprecipitation and sol-gel methods. It is established that Ce and Zr oxide additives increase the effective charge of palladium ions whereas La and Cs oxides lower it. The effect of metal-support interaction is stronger in samples prepared by sol-gel than by coprecipitation (C) 2002 Elsevier Science. B.V. All rights reserved.