The scope of the following paper is to reconsider and redefine the difference between cooperative and full function Joint Ventures under the meaning of the EU legislation. For this purpose, the work will carefully elaborate an exhaustive definition of Joint Venture and attempt to draw a broad picture of the different ways in which firms may enter into such cooperative agreements. Consequently, it will be discovered that the difference between cooperative and full function Joint Ventures is not clearly defined. Therefore, this lack of clarity could also mislead the European regulator. The risk is that the parties could build a full function Joint Venture with the scope of making an illicit horizontal agreement, for which there is no adequate sanction under the EC Merger Regulation (139/2004).