In this work, the influence of the anodic material on the electrolysis of wastewaters polluted with nitrates is studied in non-divided electrochemical cells. Conductive-diamond (CDE) and oxygen dimensionally stable anodes (DSA-O(2)) were chosen as models of anodes to study this influence. Ammonium ions, nitrite and nitric oxide were found as the main species involved in the electrolysis of nitrates in sulphate media with both anodes, but CDE was found to lead to a highly more-efficient electrochemical removal of nitrate than DSA-O(2). The huge differences observed for both anodes indicate an important role of electro-generated species in the overall reactivity of the system. In this work, the influence of these species is described, and the observed effect is explained in terms of the chemical and electrochemical reactivity of nitrogen species. (C) 2011 Elsevier B.V. All rights reserved.