The influence of low partial pressure of hydrogen on carbon nanofibers (CNFs) properties has been studied in the synthesis by methane catalytic decomposition, with the purpose of using them in polymer electrolyte fuel cells as electrocatalyst support. Using CNFs in this kind of application presents a good perspective to improve the fuel cell overall performance. CNF growth in the catalytic decomposition of methane and the characteristics which are typically required in a carbonaceous support, are influenced by hydrogen concentration, which has been studied at different temperatures. The textural, morphological and structural characteristics of the obtained CNFs have been determined by nitrogen physisorption. X-ray diffraction, electron microscopy and thermogravimetry. Electrical conductivity of CNFs has been measured compressing the powder and using a two-probe method. It was observed that low values of partial pressure of hydrogen in methane influence positively structural ordering of CNFs, and in turn improve electrical conductivity, with a slight influence on textural properties leading to highly mesoporous carbon. (C) 2008 Elsevier B.V. All rights reserved.