Electrochemical response of nitrate reduction was analyzed using Boron Doped Diamond (BDD) films grown with different boron levels and it was correlated with the electrode physico-chemical properties. X-ray photoelectron spectroscopy and contact angle measurements showed the evolution of oxygen content and the weattability associated to the chemical surface modification as boron content increase in such films. Raman spectroscopy showed that the broad peaks at 1220 and 500 cm(-1) become more evident with the boron addition. Electrochemical measurements by square wave voltammetry for nitrate reduction showed a strong dependence between the doping level of the BDD film and the nitrate detection. BDD film grown with B/C ratio of 20,000 ppm presented the best sensibility to low concentration of nitrate. This result was analyzed from the linear relationship between the peak currents as a function of the nitrate concentration. This behavior was attributed to the changes in the diamond surface chemical and the film grain size. (C) 2009 Elsevier B. V. All rights reserved.