Two different enhancement manners of Re and Mo additives have been studied in liquid phase methanol reforming with water over SiO2, ZrO2 and TiO2 supported Ir catalysts. In the cases of Ir-Re/SiO2 and Ir-Re/ZrO2, hydrogen formation rate was accelerated remarkably by the formation of some nanocomposites between Ir and Re. On the other hand, in the case of Ir-Mo/TiO2, the formation of thin monolayer-like structure of MoO2 on TiO2 surface was important for the acceleration of hydration process of partially dehydrogenated methanol with adsorbed water which was activated over thin MoO2 overlayer. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.