Vapour grown carbon nanofibres (VGCNF) were surface modified through cold oxygen plasma treatment under reduced pressure. The fibre morphology was studied by SEM (scanning electron microscopy) and HRTEM (high resolution transmission electron microscopy). The nanofibres surface functionalisation was elucidated by NaOH-titration, contact angle and surface energy measurements of the carbon nanofibres before and after plasma treatment. Oxygen plasma treatment introduced oxygen containing functional groups (hydroxylic, carbonylic and carboxylic groups) onto the fibre surfaces and also enhanced the fibre surface porosity (by etching) as well as the surface energy. There is yet to be mentioned that the fibre modifications have to occur only in the first few atomic layers. The plasma treatment can be proposed as a suitable method to change nanofibres surface from hydrophobic to hydrophilic. (C) 2003 Elsevier B.V. All rights reserved.