The formation and stability of surface species generated in the interaction of ethanol and ethanol–water mixture with Al2O3 and CeO2-supported noble metal catalysts were studied by FT-IR, TPD and TPR methods. It was found that water enhanced the stability of ethoxide surface species formed in the dissociation of ethanol. Dehydrogenation of molecularly adsorbed ethanol was proposed as a key reaction step. The TPD spectra of ethanol adsorbed on supported noble metals exhibited a high temperature desorption stage which was explained by the formation and decomposition of surface acetate species. Ethylene (product of the dehydration of ethanol) was mainly formed on Al2O3-supported noble metals, while on CeO2-supported noble metals significant amount of acetaldehyde (originated from the dehydrogenation of ethanol) was also formed. In the steam reforming of ethanol the selectivity of H2 formation decreased but that of C2H4 increased in time, while the conversions were stable on alumina-supported noble metals. These observations were explained by the inhibiting effect of surface acetate species.