Abstract The carbon-carbon dioxide reaction was used as a typical example of carbon-gas reactions for a definite confirmation of the active site concept. This concept is based on the determination of intermediate C(O) surface complexes by temperature-programmed desorption (TPD) of samples, which are quenched from reaction temperature. In detail, it is shown that two C(O) surface complexes are formed, but only the labile complex is operative at reaction temperatures up to 1000°C. Reaction rates based on the concentration of the labile C(O) surface complexes are shown to be independent of carbon conversion. As it was already found in earlier studies that these specific rates are also independent of the partial pressure, the active site concept is concluded to be definitely confirmed now.