A new model is applied to the study of Cu deposition on Ag(111). It links elements from the embedded atom model and Monte Carlo simulations. In agreement with the experiment, the present results favor overpotential upon underpotential deposition. A diffusion coefficient of 1.93 x 10(-6) cm(2) s(-1) is estimated for the system. The predicted structure of the adsorbed monolayer is more compact than the electrochemical observation, a fact which may be due to some simplifications of the model like neglecting the solvent and anion effects or the nature of the potentials employed.