UV and vacuum UV plasma photo-oxidation has been demonstrated by X-ray Photoelectron Spectroscopy (XPS) to be a controlled, dry procedure for introducing oxygenated functional groups (C-O-C, C=O, O-C=O and O=C-O-C=O) on the surfaces of multi-walled (MWNT) and single-walled (SWNT) carbon nanotube powder without the generation of liquid waste as from the traditional bulk processing method involving acidic oxidation. SWNTs produced higher levels of oxidation with shorter treatment times than MWNTs.