The European Union’s climate mitigation is highly dependent on member state compliance with EU climate policy. This paper therefore investigates the effect of different factors on national compliance with the EU’s emission target of a 20 percent reduction of greenhouse gas emissions by 2020 compared to 1990. This target is further divided into additional ones, covering different sectors: a 21 percent reduction of greenhouse gases by 2020 compared to 2005 in the sectors covered by the Emissions Trading System (ETS), and differentiated targets for each member state under the Effort Sharing Decision (ESD) during the same period. Common operationalizations of compliance in quantitative research are associated with problems since the available data mostly concern policy output. This paper measures compliance in terms of outcome instead, by comparing the emission targets to the actual reductions made by the member states. The results indicate that compliance with the nation-specific targets in the ESD sector is mostly decided by how much a state is required to reduce their emissions. Regarding the ETS target, compliance appears somewhat likelier in member states where a larger share of citizens are members of an environmental organization, and a little more unlikely in states where the industry contributes economically with a larger share of GDP.