Decision-making in the European Union is a complex phenomenon and often difficult to articulate with clarity and conciseness, both because of the numerous stages and institutions involved, and because of the important variations it carries, depending on the concrete situation in which it is applied. Thus, without wishing to enter into this issue in this abstract, for which we have reserved a distinct place in our study, we can generally state that this decision-making process presents a rule applicable to the adoption of legislative acts and represented by the ordinary legislative procedure, numerous exceptions represented by special legislative procedures, but also other configurations represented by the procedures for the adoption of non-legislative acts, implementing acts, acts of each institution, issued in the exercise of their attributions, inter institutional documents, agreements concluded by the Union with third parties (a procedure finally governed by the Treaties) and, last but not least, enhanced cooperation. The cooperation in question is a special area of research, as they not only allow states wishing to deepen integration in a certain area to a higher level than the general one but also give the possibility of building their own decision-making mechanisms. A special case, which in turn presents both similarities and differences in the situation of enhanced cooperation, is the Permanent Structured Co-operation, regulated in the EU primary law and translated into reality, relatively recently, by 25 Member States, including Romania. Taking into account the actuality of this subject, in this study we bring to your attention the main elements of the specific decision-making process of this Co-operation that addresses the field of defense. [ABSTRACT FROM AUTHOR]