What are the key determinants behind how member states develop positions for the negotiations in the Council of the European Union? This is the major question that this thesis seeks to answer. In order to develop negotiation positions for the Council, all member states have established an EU coordination system which can be defined as a structure containing interlinked units whose function is to align national EU-related activities so that a national negotiation position can be presented in negotiations in the EU decision making system. A number of studies have investigated EU coordination systems and their determinants. By and large, existing studies find that EU coordination systems vary to a large extent because they are a function of pre-existing institutions and values characterising the political systems of each member state. However, these studies are not calibrated to single out exactly which national institutions matter most and many of them neglect national agency. In order to address this shortfall and advance our knowledge about EU coordination, a number of predictions are generated using the veto player approach. The predictions are assessed against empirical evidence from Germany and Denmark, which varies considerably in terms of the constellation of veto players. The two coordination systems are outlined, using process tracing, from three perspectives. First, a diachronic perspective is taken to analyse how coordination systems were established and have changed over time. This analysis shows that veto players play a prominent role in shaping coordination systems, as they utilise their veto powers to increase their influence when determining national negotiation positions. Second, a synchronic perspective is used to examine how coordination systems are organised at a specific point in time. The veto player approach performs well in explaining cross-country variation in the role of subnational units and national parliaments. Third, an applied perspective is used to analyse how EU coordination systems work de facto when establishing national negotiation positions for the draft Services Directive. This analysis indicates that veto players are important but there is not a straightforward correlation between their number and the effectiveness of the coordination systems.