Two series of WO x /ZrO2 samples are prepared by equilibrium adsorption from H2O2 solutions at pH 1.8 containing two different precursor anions, [W2O3(O 2)4(H2O)2]2- and [H 2W12O40]6-. 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 H2O 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 2O2 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 [H2W12O 40]6--H2O2 system and by impregnation with aqueous solution of ammonium metatungstate are investigated by FT-IR spectroscopy of CO adsorbed at 80 K. © Springer Science+Business Media, LLC 2007.