VOPO4.2H(2)O supported as a mono-layer on TiO2, Al2O3 and SiO2 and as a multi-layer on TiO2 has been investigated for the oxidative dehydrogenation of ethane to ethylene in the temperature range 450-550 degreesC. The catalysts have been characterized with X-ray diffraction patterns (XRD), BET surface area measurements and electron paramagnetic resonance (EPR) and temperature programmed reduction (TPR) techniques comparing their properties to those of bulk VPOP4.2H(2)O. TiO2 promotes the best dispersion of vanadyl phosphate for mono-layer catalysts, whereas the formation Of VOPO4 bulk-like particles has been detected for SiO2 supported mono-layer catalyst or when the coverage far exceeds the mono-layer on TiO2. A fraction of vanadium is present as V(IV) in all catalysts, probably as VO(H2O)(2+)-O-P species. Reducibility of vanadium phosphate is enhanced by deposition on supports in extent depending on the strength of the interaction support-active phase, TiO2 mono-layer catalyst being the most reducible. The improvement of catalytic activity for supported catalysts has been related to the increase of both surface area and reducibility with respect to bulk VOPO4. Ethylene selectivity increases with the temperature only for well dispersed samples due to a significant increase of V(IV) containing sites at 550 degreesC observed for these samples. (C) 2003 Elsevier Science B.V All rights reserved.