The electrochemical behavior of Cu(111) and Cu(100) in 0.1 M NaOH solution in the underpotential region of Cu2O formation has been investigated by cyclic voltammetry and EIS (differential capacitance) measurements. By the analysis of differential capacitance versus potential and differential capacitance versus frequency cur Ives it is shown that the process of OH- species adsorption/desorption, takes place on both faces of the copper substrate. It is also shown that, on Cu(111), slow reconstruction of the original surface occurs during the process of OH- species adsorption/desorption, while on Cu(100), this process was found to be very fast involving a much greater amount of adsorbed OH-species.