The author carries out an analysis of the most debatable issue of the theory of constitutional law -namely, the subject of constitutional law as the branch of legal science. Professors of the Department of Constitutional Law of the MSAL Y.N. Umansky, A.A. Bezuglov, A.K. Makhnenko, O.E. Kutafin, E.I. Kozlov, N.A. Mikhalev, V.I. Fadeev devoted their studies to the subject of constitutional law. They mainly shared the same views on the content, nature and characteristics of the subject of constitutional law and their views now constitute the basis for the development of the constitutional and legal science enhanced by modern scholars of the Department -scientific adherents of the scientific school of issues concerning the subject of constitutional law. The article characterizes the peculiarities of the subject of constitutional law that distinguish it from the other branches of law. The author justifies the dual nature of the subject of constitutional law. Analyzing different opinions of scholars that primarily represent either narrow or broad approaches to the definition of the subject of constitutional law, the author notes that the adherents of O.E. Kutafin and E.I Kozlova scientific school distinguish the foundations of the constitutional system of the Russian Federation, the foundations of the legal status of the individual, the central government system and the local self-government system in the content of the subject of constitutional law. The author criticizes the views of the scholars who consider that enshrining the foundations of the social system in the Constitution is a totalitarian tradition. She also criticizes the opinion that constitutional law is not only a «common» branch of law, but that it is also a «general part of the whole Russian law» that has «a cumulative subject representing all branches of Russian law». In addition, the article criticizes the approach under which constitutional law is considered to be an "integrating", complex branch of law that develops as a result of integration of related institutions and branches of law as "the part common for all branches of law" or "suprabranch". The article also addresses the issue of drawing the line between constitutional law and other branches of law, separate institutions of which are closely connected with the institutions of constitutional law. Reference is made to the changes that took place in the subject of constitutional law at different stages of the state development; the article justifies the statement that the current content of the subject of constitutional law has considerably changed and expanded; the author explains the reasons of this phenomenon.