The influence of the support nature was investigated with supported vanadium catalysts prepared by a wet impregnation method. SiO2, γ-Al2O3, ZrO2 and TiO2 (anatase) were used as supports. Two series of catalysts were prepared, the first one consisting of catalysts of composition ca. 20% wt. V2O5/80% wt. support (series 1) and the second one prepared by washing the series 1 samples with nitric acid (series 2). In the catalysts of series 1 (except 20% V2O5/80% SiO2), vanadium is represented by both monolayer species (monomeric and polymeric VOx) and crystalline V2O5 phase. When vanadium is supported on SiO2, only the crystalline V2O5 is formed. Washing the samples of series 1 with nitric acid removes crystalline V2O5 phase. Monomeric and polymeric vanadia species are more active in the reaction of formaldehyde oxidation to formic acid as compared to V2O5.