Surface oxygen complexes formed during carbon gasification with oxygen were studied by combining diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy with transient kinetic (TK) and temperature programmed desorption (TPD) techniques. It was found that lactone (and/or acid anhydride), carbonyl, and ether type complexes are formed on the carbon surface during gasification. The complexes which desorbed during the TK experiment were not detected with DRIFT. However, the complexes which are responsible for the CO2 and CO evolution in TPD were successfully identified with these combined techniques : CO2 desorption at around 900 K originates from the decomposition of lactone and/or acid anhydride, whereas CO desorption is mainly from carbonyl and ether type complexes.