V2O5-TiO2 catalysts, prepared by VOCl3 grafting into the TiO2 surface and those modified by W6+ insertion into TiO2, are characterized by XPS, XRD, EPR, SIMS, electric conductivity, DRS UV/vis, BET, ICP, and X-ray fluoresecence methods. As revealed from the catalytic activity data, the specific activity, activation energy, and turnover frequency do not depend substantially on the crystal structure of TiO2. Reoxidation of reduced vanadia species, whose activation energies coincide with that of the SCR process, seems to be rate-limiting for this process. A common reaction mechanism is assumed for the SCR of NO by NH3 with and without O2. About 30% of the supported vanadia penetrates into the sublayers of titania independent on the method of vanadia introduction. -(MARSHNEVA, V. I.; SLAVINSKAYA, E. M.; KALINKINA, O. V.; ODEGOVA, G. V.; MOROZ, E. M.; LAVROVA, G. V.; SALANOV, A. N.; J. Catal. 155 (1995) 2, 171-183; Inst. Catal., Novosibirsk 630090, Russia; EN)