The influence of picolinic acid (PA) on copper deposition from a slightly acidic sodium sulphate electrolyte has been studied over a wide range of concentration and pH by cyclic voltammetry. The mechanism by which the copper electrodeposition process in the presence of PA takes place, depends on the chemistry and electrochemistry characteristics of the additive. Depending on the PA concentration and pH of the solution, five different cathodic current peaks are obtained, which are assigned to different steps involving copper deposition from free-Cu2+ ions and [Cu(PA)(n)](2+) complex species as well as H+ ions electroeduction. Fine-grained, highly adherent and bright copper deposits were obtained. (c) 2005 Elsevier Ltd. All rights reserved.