Carbon black and active carbon were fluorinated by exposure to CF4 plasma. Their surface chemical structures were studied by means of elemental analysis, X-ray photoelectron spectroscopy, and inverse gas chromatography as a function of treatment time. Fluorine is mainly introduced onto the carbon black and active carbon surfaces during the CF4 plasma treatment. The amount and type of carbon-fluorine (C-F) functionality formed on the surfaces of the carbon materials depends on the C-C framework structure as well as the plasma treatment time. C1s chemical shifts caused by C-F bonds on the fluorinated active carbon and carbon black surfaces are slightly different from those reported on the various types of fluorinated organic polymers, and have a somewhat ionic character. For the fluorinated active carbon the C-F bond is relatively stable, whereas for the fluorinated carbon black the C-F bond is unstable and has a significant ionic character. In addition, CO2 gas adsorption characteristics on the fluorinated active carbon can be controlled by the surface C-F functionality.