This paper analyses the impact of population growth on CO2 emissions in European Union countries. Traditionally, researchers have assumed a unitary elasticity of emissions with respect to population growth. In this study population is treated as a predictor in the model, instead of being included as part of the dependent variable (per capita emissions), thus relaxing the above-mentioned assumption of unitary elasticity. We also contribute to the existing literature by taking into account the presence of heterogeneity in the sample and considering a dynamic specification. The sample covers the period 1975-1999 for the current European Union members. Our results show that the impact of population growth on emissions is more than proportional for recent accession countries whereas for old EU members, the elasticity is lower than unity and non significant when the properties of the time series and the dynamics are correctly specified. The different impact of population change on CO2 emissions for the current EU members should therefore be taken into account in future discussions of climate change policies within the EU.