The structure of vanadium oxide overlayers of V₂O₅/SiO₂ catalysts prepared by chemical vapour deposition (CVD) and impregnation methods has been determined by using vanadium K-edge EXAFS and XANES. The Fourier transform of EXAFS for the vanadium oxide overlayers obtained by CVD of VO(OC₂H₅)₃ showed very weak peaks due to V—O—V bonds, even at the high loading level of V₂O₅(17 wt.%), while crystalline V₂O₅ gave strong peaks due to V—O and V—O—V bonds. On the basis of the EXAFS and XANES results, it has been concluded that the vanadium oxides obtained by the CVD method were present as thin overlayers on SiO₂, and were stable to calcination at 773 K. On the other hand, with an impregnation method, XANES of V₂O₅/SiO₂ at loading levels less than 5 wt.% gave peaks different from those of crystalline V₂O₅. It was presumed that an isolated V species was formed as reported in the literature. At loading levels >5 wt.%, XANES and EXAFS for V₂O₅/SiO₂ catalysts prepared by the impregnation method were very similar to those of crystalline V₂O₅, indicating that crystallites of V₂O₅were formed on SiO₂ in this case. This occurs because aggregates of vanadium compounds, e.g. oxalate, were formed as precursors of V₂O₅ during the drying process.