Owing to its unique properties such as chemical stability, large potential windows of water stability (up to 3 V) and mechanical resistance, boron-doped diamond (BDD) thin films have been widely used as electrodes for electro-analysis and electrolysis. In this work we have studied surface structural modifications in BDD thin films grown by hot filament chemical vapor deposition (HFCVD) due to usage as anodic working electrode in H3PO4 aqueous solution (pH-1, 2) up to 1000 h. With the powerful tool of Micro-Raman spectroscopy we show nonuniform structural variations of the diamond lattice. Modifications in the electrochemical properties has been observed while BDD electrodes were used as anodes. Moreover, by modelling the Fano interaction between discrete phonon states and the degenerate continuum of states, we point out an increase of the acceptor levels as a function of the electrode working hours. These experimental evidences indicate an anomalous behaviour of hydrogen loaded in the films during the growth process. A model based on the hydrogen boron interaction could explain the observed modifications in Fano coupling. (c) 2004 Elsevier B.V All rights reserved.