The surface properties of a series of V 2 O 5 catalysts supported on different oxides (Al 2 O 3 , H-Na/Y zeolite, MgO, SiO 2 , TiO 2 and ZrO 2 ) were investigated by transmission electron microscopy and FTIR spectroscopy augmented by CO and NH 3 adsorption. In the case of the V 2 O 5 /SiO 2 system TEM images evidenced the presence of V 2 O 5 crystallites, whereas such segregated phase was not observed for the other samples. VO x species resulted widely spread on the surface of Al 2 O 3 , H-Na/Y zeolite, MgO and SiO 2 , whereas on TiO 2 and ZrO 2 they are assembled in a layer covering almost completely the support. Furthermore, evidences for the presence in this layer of V-OH Bronsted acid sites close to the active centres were found. It is proposed that propene molecules primarily produced by oxydehydrogenation of propane can be adsorbed on this acid centres and then undergo an overoxidation by reaction with redox centres in the neighbourhood. This features could account for the low selectivity of V 2 O 5 /TiO 2 and V 2 O 5 /ZrO 2 catalysts.