A self-assembled monolayer (SAM) modified by 4-formylphenylboronic acid was formed on the gold electrode, which was applied for the determination of trace concentrations of Cu(II). The formation of advanced SAM on the gold electrode was evidenced by electrochemical impedance spectroscopy, atomic force microscopy and contact angle measurements. Electrochemical determination of Cu(II) ions was performed by square wave voltammetry. Some mutual interferences caused by Cd(II), Co(II), Fe(II), Ni(II) and Pb(II) ions were investigated and it was demonstrated how the negative effects of these interfering ions could be eliminated by adjustment of proper parameters of square wave voltammetry. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.