The article investigates the role of institutional structures in organizing Russian regional parliaments' activities, with the material of the Perm Oblast Legislative Assembly examined. On thoroughly analyzing the correlation of formal and informal institutions as means of aggregating interests in the Perm Oblast legislature, the authors come to the conclusion that there has arisen a kind of an "institutional hybrid" in which the formal and the informal elements are interwoven in a complicated and contradictory way. The sources of this phenomenon, in their opinion, can be traced back to the "import of institutions" that was taking place in the 1990s in the process of radical transformation of the Russian political system and adoption of formal rules, Western by their origin. According to the researchers' inference, in those Russian regions which have retained competitive milieu, no direct rejection of "imported institutions" ever took place; having been reinterpreted by political actors and built into the existing informal structures, such institutions play a real role in parliamentary interaction.