A novel aqueous method was used to synthesise mixed chromium-vanadium oxide hydrates with various chromium content, via the reaction of peroxo-polyacids of chromium and vanadium. The resulting materials are gelatinous. The dehydration of the gels result in a brown coloured amorphous powder. Depending on the chromium content, the compounds have a different characteristic crystallisation temperature upon the further heating. The crystalline compounds, except for the low chromium ones, go on a phase transition and decompose with increasing temperature.By refining the XRPD measurement data of the compounds, the type and parameters of the unit cells were determined. The experimental data were in concordance with the calculated values, using the PWC code. The lattice parameters and the crystalline structure were changed with the variation of chromium content.