A series of electrochemical impedance experiments has been carried out in order to investigate the effect of cell composition and geometry on the determination of electrochemical characteristics of strontium-doped lanthanum cobaltite (La0.6Sr0.4CoO3-delta) cathodes. The impedence responses at different electrode potentials of the half-cell and symmetric single-cell setups are compared and analyzed by the equivalent circuit modeling method. The deconvolution of impedence spectra for single cells has been achieved by a differential impedence real part vs ac frequency plot analysis method. The results indicate that the three-electrode half-cell configuration is more suitable for fundamental research of material parameters at different electrode potentials (measured vs Pt vertical bar O-2 reference electrode), whereas the simpler two-electrode single-cell setup allows the estimation of cathode performance in approximate working conditions. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.3043421] All rights reserved.