Two series of nanostructured materials were obtained by the reverse microemulsion method. It was confirmed obtaining of the nanometric crystallites of Co-substituted ceria solid solutions up to 15 mol% of Co, while the reverse oxide system was biphase, even at so low content of CeO2 as 1 mol%. The differences in pores structure of the both series were observed as well as the size of crystallites, however limited within nanometric range. The biphase materials showed higher catalytic activity than the solid solutions of Co in ceria phase, though this activity increased with Co content in CeO2 phase. (c) 2012 Elsevier B.V. All rights reserved.