The preparation of a CeO2-ZrO2 mixed oxide of composition Ce0.8Zr0.2O2 with its characterization and its use as a catalyst in the oxidation of isobutane is reported, and compared with the reactivity of pure CeO2, The formation of an homogeneous, fluorite-type solid solution is observed; the material is characterized by a higher reducibility and a higher capacity of oxygen uptake compared to pure CeO2. The catalytic activity in the oxidation of isobutane is not greatly affected by the introduction of ZrO2, but the selectivity to isobutene is significantly enhanced. This enhancement has been attributed to an increased oxygen mobility and to an increased activity for the Ce4+/Ce3+ redox couple, occurring as a consequence of the creation of surface and bulk defects in the solid solution, induced by the introduction of the smaller Zr4+ cation in the fluorite lattice.