Nanosized iron and mixed iron-cobalt oxides supported on activated carbon materials and their bulk analogues prepared by thermal synthesis are studied by X-rays diffraction, Mossbauer spectroscopy, magnetic measurements and temperature programmed reduction. Their catalytic behavior in methanol decomposition to H-2, CO and methane is tested. Phase transformations in the metal oxides affected by the reaction medium are also investigated. Changes in the reaction mechanism of the methanol decomposition after the metal oxides deposition on the support as compared to the bulk phases are discussed. (c) 2005 Elsevier B.V. All rights reserved.