"Informal institutionalization", i.e. displacement of formal institutions by informal rules, is one of wide-spread consequences of post-authoritarian (including post-communist) transformations. Russia has likewise failed to avoid it. What are then the reasons of the emergence, the mechanism of the formation, and the tendencies of the evolution, of informal institutions in Russian politics? Perfectly aware of the fact that a comprehensive answer to this question requires concerted efforts of different social disciplines, the author has made an attempt to outline some orientations for the analysis of the research problem it implies. The article consists of three parts and a Conclusion. The 1st part contains a critical review of the existing variants of explaining the domination of informal institutions in our country, and a substantiation of the necessity to complement the structural approach with the procedural one; the 2nd offers a procedural model of the informal institutionalization process; the 3d inquires into the logic of the rise and consolidation of informal institutions in the course of institutional construction (with the reform of the election process institutions as example); in the Conclusion potential effects of informal institutions are discussed, from the viewpoint of Russia's political regime's dynamics. According to the author's conclusion, the "informal institutionalization" is most likely to prove to be not just a transient "defect" of Russian political regime (in the sense of a deviation from a "correct" way of development), but, rather, its long-term and fundamental characteristic.