Aleksey Zalesov examines the reasons for the emergence of a legal mechanism for extending patents for an invention related to a medicinal product or an agrochemical, and introduction of the institution of an additional patent. The article explains the legal approach of courts and Rospatent when extending exclusive right to an invention related to a medicinal product or an agrochemical. He concludes that Russian legislation on the institution of an additional patent will require further clarification in terms of the procedure for its issuance and invalidation.