Radio-frequency, inductively coupled, non-equilibrium plasmas of oxygen and ammonia were found to be a rapid and contaminant-free method by which functional groups could be introduced onto the surface of carbon (pyrolytic graphite and glassy carbon) electrodes. These functional groups provide sites for further attachment of molecules/ions employing conventional chemical reactions. Evidence is presented which suggests the formation of a variety of functional groups using the radio-frequency method and that the species in the plasma discharges were capable of modifying basal as well as edge plane surfaces. Substrate modification appeared to be confined to the surface region without causing structural damage or any adverse electrochemical response. Attempts to brominate pyrolytic graphite using a hydrogen bromide plasma were not successful.