A global 3D-chemistry-transport model is applied to study the magnitude and geographical distribution of the in situ photochemical CO2 production in the atmosphere. In the model 1823 TgC/y of reactive carbon compounds (RCC) are emitted at the surface on global and annual average. 46% of the RCC source is released by the vegetation, 27% from biomass burning, and 27% from fossil fuel incomplete combustion. Of these, 1213 TgC/y are oxidized to produce CO2. Physical removal of the emitted species represents a loss of 154 TgC/y; wet and dry deposition of intermediate oxidation products account for approximately 360 TgC/y. The relative importance of different reaction pathways is assessed. Sensitivity experiments indicate that only 30% to 45% of the RCC emitted are oxidized to CO2. Interhemispheric gradients of CO2 at the Earth's surface produced from RCC, including photochemistry and physical removal, are compared to CO2 gradients from RCC assuming that 100% of the RCC are released as CO2, common in CO2 inverse models. A maximum difference of 0.3 ppmv in the CO2 gradients is revealed, a result of potential significance for carbon cycle studies.