Potentiodynamic electrochemical impedance spectroscopy has been applied to examine cation specific effects in anodic behaviour of platinum in 3M aqueous solutions of LiCl, NaCl, KCl and CsCl. Double layer capacitance was slowly varying with potential between "double layer" region and platinum anodic dissolution and chlorine evolution, and this provided a convenient background for examination of the complementary part of the potentiodynamic ac response which disclosed strong cation effect in the variation with potential of charge transfer resistance and parameters of equivalent circuit that represented interactions beyond the double layer. (C) 2013 Elsevier Ltd. All rights reserved.