In order to investigate the nature of VOx species supported on SiO2, gamma-Al2O3 and TiO2 a combination of a theoretical study and an experimental characterization is carried out. A molecular orbital approach of the extended Huckel type is performed to measure the plausibility of different postulated VOx species (monovanadates, divanadates, polyvanadates, etc.). The experimental characterization is performed by TPR, oxygen uptake measurements and FTIR of adsorbed pyridine. Both theoretical and experimental results indicate that the structure of VOx and its interaction with the support are strongly influenced by the nature of the oxide carrier. On TiO2 and gamma-Al2O3 dimers are the most abundant species, while on SiO2 only monomers are formed. (C) 2002 Elsevier Science B.V. All rights reserved.