In this study, two mixed electronic ionic conducting (MIEC) cathode materials, La0.68Sr0.3FeO3-delta and La0.68Sr0.3Co0.2Fe0.8O3-delta, are characterized by electrochemical impedance spectroscopy. The chemical surface and diffusion coefficients of both cathode materials are obtained directly from impedance measurements performed on full anode-supported solid oxide fuel cells. This is done by a combined distribution of relaxation times and an equivalent circuit impedance analysis method, which allows a high resolved identification and deconvolution of each single polarization mechanisms contributing to the overall loss of the cell.