The effects of exposing winter-grown tomato {Lycopersicon esculentum L.) to various sunlight irradiances and CO2 concentrations, on dark respiration (Ro), night respiration (/?},}), net photosynthetic' rate (P^), dry matter production (DMP), yield earliness and yield amount were studied. Plants were grown in greenhouses under controlled temperatures and exposed to: fiill (FS) oř half (HS) sunlight irradiance in combination with atmospheric (A) oř enriched (E) concentrations of 300-330 or 1400-1500 g(C02) m'^, respectively. The of intact leaves at noontime reached 10.7, 15.2, 5.9 and 9.6 pmol(C02) m-2 s-i in treatments of FSA, FSE, HSA and HSE, respectively. The irradiances on the upper leaf surface during the measurements ranged between 160-190 and 450-550 pmol s'^ in the HS and FS treatments, respectively. of leaves which were kept in darkness following the measurement amved at efflux of 2.6, 2.5, 1.4 and 1.4 pmol(C02) m‘2 s'* while their Pn G^etween 20:00 and 24:00) reached values of 0.9, 1.3, 0.8 and 0.8 pmol(C02) treatments of FSA, FSE, HSA and HSE, respectively. Elevating the CO2 concentration from 300 to 1500 g m'^ increased P^ by 16, 28, 30 and 46 % under an irradiance of 160 pmol m‘2 s'*, and 19, 34, 59 and 44 % under irradiance of 320 pmol m-2 s'* in the FSA, FSE, HSA and HSE treatments, respectively. Increasing the measurement irradiance from 160 to 320 pmol m'2 s'* enhanced P^ by 69, 78, 23 and 49 % in an atmosphere of 300 g m-^ CO2, and by 73, 84, 49 and 47 % in an atmosphere of 1500 g m-^ CO2, in the FSA, FSE, HSA and HSE treatments, respectively. DMP was strongly influenced by the different environmental conditions and the total dry matter accumulation in the shoot per plant during 145 d reached 580, 347, 398 and 235 g in the FSA, FSE, HSA and HSE treatments, respectively. CO2 emichment promoted early yield under both full and partial sunlight irradiance. The HSE treatment led to earlier yield harvesting than the FSA and HSA treatments. The yield of the seven first trusses reached 6.8, 4.6, 5.7 and 3.2 kg per plant in the FSA, FSE, HSA and HSE treatments, respectively. Some increase in fruit fresh matter and diameter of fruits was detected in the C02-enrichéd treatments as compared to the non-enriched ones. Thus the combination of moderate shading and CO2 enrichment might provide a more productive option for winter- grown tomatoes in regions of subtropical climate, even in the winter, than the conventional management of aerated greenhouses without CO2 enrichment which are exposed to fiill sunlight.