The European Union (EU) diplomatic system can be conceived as representative of a system of governance, and, through this, of its constitutive independent units. The way in which the EU's political system is represented through diplomatic practices is telling of two interrelated aspects of the EU's international actorness. First, it reveals the link between the foreign policy of a non-state actor and sheds light on the division of competences that characterises the EU's foreign policy-making system. Second, it highlights the complex institutional and organisational features of a non-state diplomatic system. This article locates the puzzle of EU diplomatic activity in the general debate about changes in the institution of diplomacy. Secondly, it explains how post-Lisbon institutional arrangements have been translated into practice in two multilateral delegations: the delegation to the UN and the mission to the WTO in Geneva. It finally draws some preliminary conclusions. The article concludes that beyond competition over the attribution of competences in the EU’s diplomatic governance, different ideas coexist about what ‘locating the EU in the international scene’ means. Pursuing a ‘single voice’ by unifying forms of external representation is not necessarily perceived as the most convenient strategy envisaged by all EU actors. While institutional actors tend to believe that coherence and strength may descend from a more unified system of representation, the member states tend to believe that, in certain circumstances, differentiation could increase the EU’s strength.