In the present article a molten carbonate fuel cell (MCFC) system has been developed, modeled and implemented in Matlab language. It enables definition of the optimal operating conditions of the fuel cell, in terms of electrical and thermal performance, when it is a part of a hybrid plant composed of an MCFC system, a gas turbine and a possible heat recovery system. The thermal energy, which is recoverable from the adequately treated anodic exhaust gases, is utilized in a gas turbine plant to reduce its fuel consumption. Therefore, in the present article a methodology is illustrated to calculate the optimal values of some parameters characterizing the MCFC/gas turbine integrated system in terms of the electrical, first law and equivalent efficiencies. A choice is made among the sets of values of parameters investigated to improve the performance of the same integrated system according to its use (for the production of electric energy only or for the contemporary production of electric and thermal energy). Copyright (C) 2010 John Wiley & Sons, Ltd.