The vacuum-uv photolysis of CO2 containing initially no oxygen was investigated in a closed system and the quantum yields of ozone and oxygen determined. The quantum yield for ozone production was found to be below Q(O3) ≤0.03, which is insufficient to explain the oxygen deficiency observed in the O2 quantum yields. The [O2]/[CO] ratio was found to depend on the light intensity, on the time interval after which an irradiated sample was subjected to analysis, and on the ratio of carbon dioxide to admixed rare gas concentration. The results concerning the [O2]/[CO] ratio can be explained by the formation of CO3 due to the attachment of 1D oxygen atoms to CO2. This reaction is in competition with the third-body recombination of 1D oxygen atoms.