The increase of atmospheric CO, concentration influences climate changes. The road transport sector is one of the main anthropogenic sources of CO, emissions in the European Union (EU). One of the main parameters influencing CO2 emissions from passenger cars (PCs) is their weight. which increases during last years. For the same driving distance, heavier vehicles need more work than lighter ones, because they have to move an extra weight, and thus more fuel is consumed and thus increased CO, emissions. The weight control of new PCs could be an efficient way to control their CO, emissions. After an analysis of the EU new PCs market, their segment distribution and their weight. some estimations for 2020 are presented. Based on this analysis, 13 base scenarios using several ways for the control of the weight of future European new PCs are used to estimate their CO, emissions and the benefit of each scenario. The results show that a significant benefit on CO, emissions could be achieved if the weight of each PC does not exceed an upper limit, especially if this limit is quite low. The benefit obtained by limitations of weight is higher than the benefit obtained from the expected decreased future fuel consumption. Similar results are obtained when the weight of new PCs does not exceed an upper limit within each segment, or when the weight of each new PC decreases. (c) 2007 Elsevier Ltd. All rights reserved.