We propose the following identification indicators for CO₂ of different origins based on data obtained from analyzing the molecular composition of 1198 gas samples, the CO₂ carbon isotope values of 390 samples, and the helium isotope composition of 256 samples collected from wells of 16 oil- and gas-bearing basins and gas seepages in China, and reviewing literature on organic and inorganic CO₂ throughout the world. CO₂ is of organic origin if CO₂ content <15% and ^dgr¹³C_CO2 < -10^pmil; CO₂ is of inorganic origin if ^dgr¹³C_CO2 > -8^pmil or CO₂ > 60%; and CO₂ is of either organic or inorganic origin or a mixtur of organic and inorganic origins if -10^pmil < ^dgr¹³C_CO2 < -8^pmil. In China, the ^dgr¹³C_CO2 values of organic CO₂ mainly range from -10 to -22^pmil. In tectonically stable oil- and gas-bearing basins where deep faults and magmatism are undeveloped, organic CO₂ occurs almost exclusively. In tectonically active oil- and gas-bearing basins where active faults and magmatism are present or in areas of modern volcanic activity, the ^dgr¹³C_CO2 values of inorganic CO₂ range from -2 to -8^pmil and are distributed along faults. The inorganic CO₂ with a ^dgr¹³C_CO2 value of 0 ±3^pmil is of metamorphic origin, and that with ^dgr¹³C_CO2 values of -6 ±2^pmil is mantle derived and of magmatic origin. In China, the ^dgr¹³C_CO2 values of inorganic CO₂ gas pools range from -3.41 to -8.44^pmil and the helium ratio (R:Ra) is >1, which indicates that these gases are typically derived from the mantle.