The amounts of CO2 embodied in imports to, and exports from, Japan have been estimated using input-output tables, assuming imported commodities have the same CO2 emission intensities as those of the corresponding Japanese products. The concept of the attributed CO2 emission to each country was introduced. Until 1985 in Japan, the amount of CO2 embodied in exports had been larger than that in its imports, but, by 1990, such a situation had been reversed.