Constant phase element is still an object of controversy in the literature. It replaces capacitance or pseudocapacitance at solid electrodes. In the present paper influence of experimental parameters as cell geometry, distance between the working electrode and the Luggin capillary, surface roughness, and adsorption on the CPE parameters was studied. The obtained results indicate that the main cause of such behavior is adsorption of trace impurities from solution. (C) 2011 Elsevier Ltd. All rights reserved.