The behaviour of copper in oxalic acid solutions was studied both by cyclic voltammetry and electrochemical impedance technique. It was shown that, due to the easy complexation of copper with oxalate ions, the species present in the solution depend on the pH. During the dissolution, it was shown that the electrode was blocked by the precipitation of copper oxalate. On the other hand, a model was proposed to explain the copper deposition in concentrated oxalic acid solution. We found a rather good agreement between the experimental and calculated impedances. (C) 2007 Elsevier Ltd. All rights reserved.