The impedance response of ITO electrodes with different sheet resistance R(sh)(Omega/sq) immersed in electrolytes of different conductivity is investigated under blocking conditions. The pattern observed when the electrode is much more resistive than the electrolyte resembles that typical of porous metal electrodes - in the hf limit a line forming an angle of 45 degrees with the real axis, in the lf limit a vertical line corresponding to constant values of resistance and capacitance - and is discussed with reference to the classical theory of de Levie. The pattern observed when electrode and electrolyte resistances are comparable depart from the above limiting behavior and may be reproduced by a finite elements calculations able to account for current distribution.