The catalytic behavior of nanostructured catalysts based on nickel, cobalt and cerium oxide in ethanol steam reforming (ESR) was studied to investigate the effect of the nature of the metal, their combination and the method of preparation. Mono-and bimetallic catalysts with equal metal content (M:Ce = 4: 6, M = Ni, Co, or Ni/Co = 1) were prepared by two methods, impregnation and coprecipitation within reverse microemulsions, characterized by S-BET, XRD, TPO and HRTEM, and tested for ESR at 500 degrees C. The nickel catalyst prepared from microemulsions exhibited the best performance in terms of catalytic activity (close to 100% conversion), stability and hydrogen yield. Al the other catalysts deactivated at different paces due to formation of carbon deposits. The oxidative regeneration treatment of the deactivated catalysts recovered the initial activity of the impregnated catalysts but increased markedly those of catalysts from microemulsions. Thus, the catalytic behavior in ESR of the (Ni, Co)-Ce-O system depends on the preparation method, its composition and the catalyst history.