An impedance model is developed for a porous oxygen electrode on top of a solid oxide conductor, taking into account adsorption and surface transport along the pore walls, interfacial diffusion and reaction along the interface, as well as current distribution (2D) in the electrolyte. All parameters are in principal measurable. Simulated impedance spectra typically exhibit two semicircles, one related to the charge transfer reaction at the interface (high frequencies), and one related to mass transfer limitations (low frequencies). The resolution of these two semicircles, however, depend on the relative contributions of these two processes to the overall potential losses, and the magnitude of the interfacial capacitance relative to the other kinetic and transport parameters, as well as geometrical parameters. (c) 2006 Elsevier B.V. All rights reserved.