The surface and bulk oxygen mobility and reactivity of ceria-based solid solutions as related to the process of methane conversion into syngas can be tuned in a broad limits by bulk and surface promoters. Variation of the surface/bulk real structure of those complex oxides and their strong interaction with the surface promoters (Pt, Ni) appear to be responsible for those effects. (C) 2004 Elsevier B.V. All rights reserved.