Reducing greenhouse gas emissions is one of the main objectives of current environmental policy. Recent debates again and again raised the point of CO 2 emissions of electricity generating technologies not employing combustion of fossil resources. This argument often focuses on the use of nuclear power.On the basis of existing studies and publications about CO 2 emissions in nuclear power, fossil-fired power plants, and renewables, the article compares the methodological approaches used in life cycle analyses and their findings. Construction of the power plants, their operation, maintenance, and disposal at the end of their useful lives require materials, services, and auxiliary energy. In the case of nuclear power use and electricity generation from fossil sources, there are also the expenses incurred for providing the necessary fuels. Establishing a complete energy and CO 2 balance of one specific technology takes a holistic approach over the entire life cycle. The article falls back upon existing studies and publications and compares the methodological approaches used and findings made. It turns out that, for all energy technologies, CO 2 emissions of upstream and downstream chains are low compared to those arising during operation in the combustion of coal, oil, and gas. The assumption often heard that the use of nuclear power gave rise to considerable CO 2 emissions as a result of fuel supplies is not correct.