Chemical and structural modifications induced by protons at the surface of polyacrylonitrile and carbon nanotube/polyacrylonitrile composite films are analysed by TEM, profilometry, IR and XPS. Changes induced in the film ate related to the energy of incident particle and implanted dose. The irradiation of the composite films induces the emergence of the nanotubes outside of the polymer but with no increase of the surface roughness. Spectroscopic modifications in both films are globally similar, the most significant feature being a lower relative concentration of nitrogen with respect to carbon close to the surface. (C) 2003 Elsevier Science B.V. All rights reserved.