The behavior of the electrode systems M,O2/O2 (M = porous Pd, Pt, A and dense In2O3; O2− = ZrO2-based single-crystal solid electrolyte) was studied by means of impedance measurements. The examination of the Pt,O2/O2− electrode system showed that the constant phase element (CPE) can be attributed to a nonuniform distribution of current at the electrode surface. It was observed that the CPE parameters n and B in the expression YCPE = B (jω)n may be related by B=(Cdl)n (RΩ)n-1, where Cdl is the double layer capacitance and RΩ the resistance of the electrolyte in the cell. Then, Cdl of the electrode - electrolyte interface could be determined. The specific Cdl of the oxidized noble metals and india electrodes is nearly one order of magnitude lower than Cdl of the electrodes in the metallic state. The Cdl value of all the electrodes studied depends little or is independent of temperature and oxygen pressure. It is concluded that the Helmholtz model of double layer structure does not contradict the Cdl behavior.