In this work, we study the influence of the average crystallite size and dopant oxide on the reducibility of CeO₂-based nanomaterials. Samples were prepared from commercial Gd₂O₃-, Sm₂O₃- and Y₂O₃-doped CeO₂ powders by calcination at different temperatures ranging between 400°C and 900°C and characterized by X-ray powder diffraction, transmission electron microscopy and BET specific surface area. The reducibility of the samples was analyzed by temperature-programmed reduction and in situ dispersive X-ray absorption spectroscopy techniques. Our results clearly demonstrate that samples treated at lower temperatures, of smallest average crystallite size and highest specific surface areas, exhibit the best performance, while Gd₂O₃-doped ceria materials display higher reducibility than Sm₂O₃- and Y₂O₃-doped CeO₂.