In this paper a new model for porous electrodes in molten-carbonate fuel cells (MCFC) is presented. The model is based on an averaging technique commonly used in porous-media problems. Important disadvantages of the existing agglomerate model caused by geometric assumptions and restrictions are eliminated in this new model. Unlike the agglomerate model, the new model is suitable for studying three-dimensional and anisotropic problems and incorporating the degree of electrolyte fill. Different reaction mechanisms can easily be incorporated. The validity of the new model is checked and compared with the agglomerate model by fitting the two models to ac-impedance spectra recorded from porous MCFC cathodes.