The Russia/Soviet/Commonwealth of Independent States (CIS) collection is one of the world's great scholarly resources for the study of this area in the twentieth century and contains some of the most important holdings of the Hoover Institution. Geographically it includes Armenia, Azerbaijan, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Moldova, the Russian Federation, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan. Subject areas include twentieth-century history, politics, government, economics, military affairs, and political and social movements, especially the Russian Revolution and communism.

The collection endeavors to gather and preserve documentation within its subject and geographic areas, including monographs, periodicals, newspapers, pamphlets, government documents, ephemera, manuscript collections (such as personal papers and organizational records), films, posters, photographs, and maps. The majority of the collected materials are in Russian; however, materials can be found in all the languages of the CIS states, as well as in most Western languages.