Gas flow channels of proton exchange membrane fuel cell were highly water-proofed by plasma polymerization. Pretreatment by sandblasting was efficient for increasing water-contact angle of the coated surface. With a very low water wettability of gas flow channels, peak power of the fuel cell increased in the condition where the condensed product water tends to accumulate. (C) 2004 Elsevier B.V. All rights reserved.