The authors discuss the preservation of dissertations by national scientists in the libraries of the Russian Academy of Sciences (RAS) research institutions. A share of theses defended in the Russian Empire before 1918 makes the part of the general collection. Since 1934, the scholarly manuscripts havebeen spinned off into a separate collection, since 1950, along with theses abstracts. The dissertations were transferred to the organizations where they were defended, therefore the collection comprises the works accomplished in different institutions. This could be the only location for the manuscripts of 1930–40s, as the Dissertation Collection of the Russian State Library was established after 1944. The authors argue that apart from their information value, the dissertations make the valuable source on the history of national science and society, demonstrate communications between academic organizations and continuity of scholar schools, and are of great memorial value. The mission of libraries is to preserve the scholar legacy of this country and to support accessibility of information on dissertations through e-catalogs and digitizing full texts of the Soviet-era theses.