The aim of the study is a comparative analysis of approaches to designing and implementing an institution of regulatory impact assessment in the largest countries of the post-Soviet space - Russia and Kazakhstan, an identification of problems and prospects for the development of this institution in the countries of the analyzed population.The study was conducted using both general scientific and specialized methods. General scientific methods of comparative and evolutionary-genetic studies were used to conduct cross-national comparisons of the implantation processes of new state institutions in a historical retrospective. Specialized methods of institutional and constitutional theory allowed to analyze the mutual influence of legal and economic factors in the adoption of state decisions in the economic regulation sphere within the framework of the existing national systems of public administration.Based on the results of the study, there were drawn conclusions reflecting the specifics of designing an institution of regulatory impact assessment in Russia and Kazakhstan in terms of selecting key actors and distributing authority among them. There was noted a high role that assign to structures expressing the interests of entrepreneurs in Kazakhstan when an assessment institute designing. There is characterized the degree of maturity of the assessment institute in the analyzed countries.