Measurements of a system consisting of cathode/doped ceria diffusion barrier/doped zirconia electrolyte were made using twoand three-electrode configuration. Results obtained on a three-electrode measurement configuration were compared with and reflect the results obtained in two-electrode configuration. Three-electrode measurements allowed separating the impact of the symmetrical interface in the investigated system. They also enabled to obtain additional information about the investigated interface, such as the behavior of the system under an external polarization voltage. It has been shown that the 200 to 1200 nm thick CGO diffusion barrier layer fabricated by spray pyrolysis significantly reduces the polarization resistance of the interface. It also minimizes the impact of the polarization resistance in the presence of external polarization voltage.