The configuration of internal reforming has been successfully applied in molten carbonate fuel cells (MCFCs), allowing a flexibility in fuel use unfeasible for other kind of fuel cells, which operate at lower temperatures. On this basis, a theoretical study able to provide useful information on the use of ethanol, methanol or methane as fuel in MCFCs has been carried out. The paper reports the most significant results obtained from this comparative analysis, which allows clear evaluations about the energetic suitability of each examined fuel. This study, developed by the support of a mathematical model, gave as main results the chemical, electrical and thermal power densities obtainable by each raw fuel and evidenced the limits or gains arising from the variation of the MCFCs operative parameters. Leaving out the economical point of view, ethanol present some advantages (natural availability, storage and handling safety, heat distribution on the catalyst, etc.) compared with the other fuels.