. The starting material is amorphous zirconium oxyhydroxide. The maximum W densities obtained are larger than that reported in the literature for systems synthesized by the same method using aqueous non-peroxide solutions. In the case of the metatungstate precursor, this increase is attributed to the generation of additional anchoring sites by interaction between the amorphous support and H 2 O 2 . The high uptake achieved when the peroxo complex is used as a precursor is a result of both the ZrO x (OH) 4-2x -H 2 O 2 interaction and low nuclearity of the adsorbing anion. The materials are characterized by XRD, DR-UV-vis, Micro-Raman and FT-IR spectroscopy. The surface acidities of samples with identical W loading prepared by equilibrium adsorption from the [H 2 W 12 O 40 ] 6--H 2 O 2 system and by impregnation with aqueous solution of ammonium metatungstate are investigated by FT-IR spectroscopy of CO adsorbed at 80 K.