Interaction of hydrogen with a series of mixed oxides CeMxOy (M = Cu, Ni; 0 less than or equal to x less than or equal to 1) has been studied in the 300-1073 K temperature range. A dynamic method of titration has been used to provide evidence for reactive hydrogen H* present in the solids. This method of titration involves hydrogenation at 423 K of isoprene under helium flow in the absence of gaseous hydrogen. The hydrogen reservoir capacity depends on the pretreatment temperature under H-2 and is related to the creation of anionic vacancies in the solid. All the CeMxOy mixed oxides are large catalytic hydrogen reservoirs with marked diffusion properties of hydrogen species (H*, OH-). In the series studied, the highest amount of hydrogen H* (29.5 10(-3) mol g(-1)) is stored by CeNi0.7Oy pretreated under H-2 at 523 K (H6.8CeNi0.7Oy). In the conditions in which the incorporation of hydrogen in the solid occurs, X-ray diffraction analysis under H-2 shows shifts depending on the treatment temperature and corresponding to non-negligeable expansion of the ceria-based lattice attributed to the insertion of hydrogen species of hydridic nature in the anionic vacancies.