Radiochemical reactions between tritium and carbon dioxide molecules at elevated temperatures have been investigated. There is no significant temperature dependence of the radiochemical reactions in the temperature range from 373 to 573 K. It has been found that concentration of such reaction products as tritiated methane and carbon monoxide molecules increases with time, whereas the concentration of tritiated water molecules remains practically constant. Additionally, influence of -ray radiation on radiochemical reactions in H2 and CO2 gas mixture was examined. Water and methane molecules are formed as radiation products, however, carbon monoxide is not detectable.