In this paper, the Cu electrodeposition on boron doped diamond (BDD) electrodes was studied. The reactions and the nucleation mechanism were evaluated by analyzing the influence of different electrolytes and Cu2+ ion concentrations in the solution. The cyclic voltammetry results showed that the Cu deposition and dissolution processes were affected by the solution pH. In acidic solutions (pH similar to 2.0), the energy required to initiate the nucleation process was higher than that for the Na2SO4 solution (pH similar to 5.0). The nucleation mechanisms were examined by fitting the experimental chronoamperometric data into appropriated nucleation models. Using the model developed by Scharifker-Hill, the Cu nucleation mechanism in 0.1 mol L-1 Cu2+ ions concentration was inconclusive - independent of the pH solution. However, the Cu nucleation mechanism was conclusive in 10(-3) mol L-1 CuSO4 solutions containing Na2SO4 and H2SO4 as electrolyte. So, from (i/i(max))(2) vs t/t(max) profile, Cu instantaneous nucleation was verified. Other more complete models of nucleation like those developed by Sharifker-Mostany (SM) and Hermann-Tarallo (HT), also confirmed the Cu instantaneous nucleation, from the Cu nuclei density (N-0) determined by fitting the potentiostatic transients. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.093204jes] All rights reserved.