Crystalline CoO/Co3O4 particles with polyhedral morphologies have been successfully synthesized via a versatile spray roasting method. The feed solution was prepared using distilled water or ethanol-water mixture as solvent while CoCl2 center dot 6H(2)O as solute, and then sprayed by an inner mixed air-nozzle and roasted in an erective tubular resistance furnace with compressed air as carrier gas. The as-prepared specimens were characterized by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and FT-IR spectroscopy. The results showed that pure crystalline Co3O4 particles have been obtained under the condition of H2O was used as the sole menstruum while CoCl2 center dot 6H(2)O was used as the core materials. Meanwhile, the pure well-crystallized CoO particles with octahedron morphology were obtained successfully by dissolving CoCl2 in ethanol-water mixture solution concentrated CH3CH2OH-H2O (1:1, v/v) as reactants. The possible reaction mechanism of different solvent in the synthesis process was elucidated as well. (c) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.