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The oxidative dehydrogenation (ODH) of propane has been studied on cerium-based mixed oxides. An optimum propene yield of 5.4% is obtained at a low temperature (648 K) on CeNi0.5OY, and this yield can be increased to 6.9% by treating the solid in situ under H2. In situ "under catalytic reaction" X-ray photoelectron spectroscopy evidences that the active Ni species present the characteristic of being able to be reduced and reoxidized easily and reversibly, allowed by their close interaction with Ce species. Moreover, the results obtained by X-ray diffraction analysis performed after a catalytic test are in agreement with the presence of hydrogen species in the anionic vacancies of the solid. So, a low coordination ODH active site is proposed to involve an anionic vacancy common to two cations of different natures, X M-Y M′ (where X and Y are the numbers of unsaturation of each cation), allowing a heterolytic abstraction of a Hspecies from the alkane while the H + species leads with the O 2species of the solid to a OHgroup.