Oxygen diffusion in carbon‐doped silicon which received an extended isochronal anneal in the temperature range between 460 and 850 °C was studied. At temperatures below 690 °C, an enhanced oxygen diffusion was observed. This phenomenon has been previously suggested to be attributed to mobile stable carbon and oxygen complexes. In addition to these mobile species, it is proposed that the carbon and oxygen complexes could also act as an activated state in an enhanced diffusion process.