Nanosized cobalt mixed oxide, with high stability of Co(II), were obtained by controlled thermal decomposition of layered double hydroxides (LDHs) with Co, Zn and Al in the brucite-type sheets. The effect of the microwave ageing treatment of the LDHs into the properties of the calcined products was studied. For this reason, the precursors were submitted to increasing periods of time to microwave-hydrothermal treatment. The use of microwave ageing yields to well-crystallised compounds without oxidation of Co2+ species to Co3+. The structure features of oxides remain during whole ageing process; the microwave-hydrothermal treatment yield, in all cases, spinel-like compounds. Studies of surface properties, N-2 adsorption/desorption and the TEM micrographs, show that the textural properties are strongly modified depending on the irradiation time were submitted to, altering both the pore size distribution and the particle size of the nano-oxides. (c) 2007 Elsevier B.V. All rights reserved.