This dissertation critically assesses the current scope and meaning of participation rights in European administrative law and proposes a different normative solution to the problem of the procedural protection of rights and legally protected interests. The analysis of the Courts' case law on this matter demonstrates that their view on participation rights is determined by a bilateral conception of the procedure which involves the decision-maker and the decisiontaker and justifies the latter's right to be heard. All extensions of this right endorsed by the Courts' case law fall within the realm of this basic construction. Likewise, the exclusion of participation rights from rulemaking procedures is a consequence of this basic approach to participation rights. It is defended that the structural scheme within which the European Courts conceive participation rights prevails over the consideration of the substantive adverse effects that may be produced in the legal sphere of legal and natural persons. It is defended that this status quo is too restrictive and overlooks the procedural protection of rights and legally protected interests where this would be justified. An extension of the scope of participation rights is thus proposed. The solution defended is grounded on a concept of participation, built on the basis of rationales of participation that can be derived from the Courts' case law as well as from rules and principles of national laws, and is framed by the concept of legal administrative relationship, which was developed in national administrative law. The solution proposed is deemed to be more consonant with the rule of law, as well as with specific features of European administrative law (in particular with the characteristics of European normative acts and with the centrality of the individual conveyed by principles of European law). This study consists of two parts. First and foremost, it is an interpretation of the Courts' case law regarding participation rights, as well as of selected relevant legal provisions covering this matter. For this purpose, this interpretation combines the literal, teleological, historical and systematic elements of interpretation. The theoretical conceptions that frame the critical analysis of the Courts' stance are grounded on rules, principles and theories found and developed in selected national legal systems. These contribute to a better understanding of participation rights from a de lege lata perspective because they have inspired some of the current features of European administrative law on this matter. Furthermore, they are capable of providing a valuable second level of analysis to critically assess the current status quo. Secondly, this dissertation includes a study of those forms of participation that exist in the EU political system and that do not constitute legally enforceable rights and duties. These demonstrate that participation is a constitutive feature of the EU political system. Moreover, this permits to consider other meanings of participation, which are not fully deprived of legal meaning, to contrast them with the rights-based approach to participation proposed in this dissertation, as well as to demonstrate the little attention given to rights-based participation in European decision-making.