We describe the use of the decomposition technique for comparing energy-related CO2 emission levels between countries/regions. Application studies pertaining to total and per capita CO2 emissions for three OECD regions and three world regions are presented. These studies demonstrate how the difference in annual CO2 emission level between two regions may be expressed in terms of inter-regional differences in fuel share in energy demand, aggregate energy intensity, income, and population. We also show that the recently proposed logarithmic mean Divisia decomposition approach can be conveniently applied in such comparative studies.