The article developed here, in line with the national academic production on the discussions around federal regulatory agencies, aims to analyse the regulatory instruments adopted in an attempt to reduce the democratic deficit created in the context of the agencies. In this way, I seek to understand how the participation mechanisms with the affected agents are configured as an argument to justify the legitimacy of the agencies and all their normative production. Specifically, this paper seeks, from the Brazilian literature on the subject, to verify if the Regulatory Impact Assessment (RIA), as a process of analysis of the possible impacts resulting from the adoption of a certain measure that aims at a specific purpose, comes to reinforce the search for legitimacy of regulators. Thus, through RIAs, agencies seek to provide transparency and social participation to the technical decision-making process, providing greater efficiency and technical quality to regulatory decisions, which, ultimately, contributes to the creation of a scenario of greater legal security. Finally, the study reveals that despite the legal provision for carrying out the RIA, many times the exemption is obtained from the obligation to carry it out, thus contributing to the emptying of this regulatory process.