Carbon paper (CP) used for proton exchange membrane fuel cells (PEMFCs) are improved using carboxyl-terminated butadiene-acrylonitrile (CTBN)-modified phenolic resin (PF) for impregnation of CF preform. The effect of CTBN ratio on the properties of CP, which is fabricated by the processes of impregnation, molding and heat treatment, is investigated. The results show that compared with the CP without CTBN addition, the CTBN-modified CF exhibits significantly improved overall properties. With the increase of CTBN ratio in the mixture, porosity and permeability of the modified CF increase because of the low carbon yield of CTBN after heat treatment. Mechanical strength and conductivity also increase because of the chemical reactions between the CTBN and resin that lead to robust interfacial bonding in the CF product. However, excessive CTBN addition causes decreased tensile and bending strength of the CP. Single cell tests show that the increased conductivity of the CF enhances the polarization performance in the Ohm polarization region, while the CTBN-induced nearly spherical micro/macro-pores in the CF matrix improve the performance in the concentration polarization region. At an optimum CTBN ratio of 50 wt %, the membrane electrode assemble with the modified CF exhibits a current density of 1606.5 mA cm(-2) at 0.608 V. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.