Although not explicitly regulated by the EU treaties, EU agencies not only exist but also have increased in number and power. In addition, while EU agencies may exercise very similar functions to those of the Commission, Articles 290 and 291 of the Treaty on the Functioning of the European Union (TFEU) do not list agencies among the possible authors of non-legislative acts. The existing situation raises the questions of the extent to which the ongoing agencification in the EU is legitimate and what its limits are. This article addresses these questions in the light of the old and new Treaties and case law, including the just released ESMA-shortselling case. It shows that while the Lisbon Treaty made a few steps forward on the road of legitimizing EU agencies and delegating important powers to them, the scope of powers that EU agencies can have remains unclear. In this respect, the European Court of Justice's lenient approach in the ESMA-shortselling case is unfortunate because it neither clarifies the issue nor pushes the Union Legislator and the Member States to address it. Consequently, in the absence of clear limits, further agencification is likely to persist at the risk of increasing the democratic legitimacy deficit and remaining accountability gaps.