A fuel cell system with flow passages and/or flow chambers which conduct moist gases in operation is characterized in that at least a part of the flow passages and/or flow chambers is provided with a coating which takes up water in distributed form at low temperatures and releases the water again at least in part at higher temperatures. This coating makes it possible to operate the fuel cell system at pronounced temperatures below zero, such as, for example, -40.degree. C., and to ensure an adequate humidification of the operating gases, which protects the membranes from damage and favors a faster starting up of the fuel cell system.