Adsorbed methoxy species were observed on CexZr1-xO2 ceria-zirconia mixed compounds, with x ranging from 0 to 1. Surface cationic sites were so investigated looking at the v(OC) and v(s)(CH3) methoxy vibrations. From the v(OC) band due to methoxy species on-top coordinated with Zr4+ ions, it was concluded that mixed compounds were solid solutions with no segregation of the cations at the surface. Mixed compounds were H-2-reduced in the temperature range 473-873 K. No reduction of Zr4+ ions was observed. Conversely, the formation of surface O-vacancies in the vicinity of cerium ions was accompanied by the Ce4+/Ce3+ reduction. Cerium surface ions were completely reduced at 673 K except for samples for which x = 0.8 and 0.68. This is in accordance with an increased O-bulk mobility towards the surface as zirconia is incorporated into ceria. Re-oxidation by O-2 amounts, volumetrically measured, has shown that the reducibility of cerium cations increased with the zirconium content. This was correlated with a deeper reduction of the crystallites.