The scope of this paper is to report the results obtained about the solid state phase relations in the interfacial region for a system consisting of Y2O3-modified CeO2 solid electrolyte and Y0.7Ca0.3MnO3-based ceramic electrode. The ceria-yttria solid electrolyte has been doped with CaO for improving the grain boundary conductivity, according to the results described elsewhere. The electrode was fixed on the electrolyte by powder pressing and the sandwich was cofired at several temperatures. The microstructure was observed with Scanning Electron Microscopy (SEM), and the reaction products were established by X-Ray Diffraction (XRD) of the cofired materials. Complex Impedance Spectroscopy was used for determining the total electrical conductivity and the electrical behaviour of the interphase electrode-electrolyte. The boundary region between the electrode and the electrolyte showed no reaction phases. The complex impedance measurements indicate that the (Y,Ca) manganites have the conductivity comparable to that of the Ag electrodes.