Chromium ion-doped polycrystalline titania catalysts, mainly used in photoreactions, were studied by Fourier transform infrared (FTIR) spectroscopy and by X-ray photoelectron spectroscopy (XPS). Two series of catalysts prepared by two different methods, i.e., coprecipitation and impregnation, were analysed. The FTIR spectra recorded upon adsorption of ammonia and after outgassing at increasing temperatures indicated that Cr(x)O(y)/TiO2 samples, whichever preparation method was used, have two types of surface acid sites, Lewis and Bronsted sites. The Bronsted sites are associated with the presence of chromium, since they were not detected in pure titania. According to the X-ray photoelectron study, Cr(III) and Cr(VI) species are present in both series of catalysts, with the higher oxidation state being quite unstable under X-rays. As shown by quantitative XPS analysis, only the catalysts prepared by coprecipiatation and containing up to 2% Cr can be described by the Kerkhof-Moulijn monolayer model.