The efficiency of a solid polymer fuel cell (SPFC) system operating on ethanol fuel has been analyzed as a function of operating parameters focusing on vehicle and stationary applications. Two types of ethanol processors - employing either steam reforming or partial oxidation (POX) steps - have been considered and their performance has been investigated by thermodynamic analysis. SPFC operation has been analyzed by an available parametric model. It has been found that dilute ethanol-water mixtures (similar to 55% v/v EtOH) are the most suitable for stationary applications with a steam reformer (SR)-SPFC system. Regarding vehicle applications, pure ethanol (similar to 95% v/v EtOH) appears to be the best fuel with a POX-SPFC system. Efficiencies in the case of an ideal ethanol processor can be of the order of 60% under low load conditions and 30-35% at peak power, while efficiencies with an actual processor are 80-85% of the above values.