This collection comprises over 30 running meters of files (2,249 archival units) of paper copies and nearly 700 archival units of digital copies obtained from various institutions, including from the Separated State Archives of the Security Service of Ukraine, the Supreme Prosecutor's Office of Ukraine in Kiev, the Lithuanian Special Archives in Vilnius, the Archives of the Ministry of the Interior of Georgia, the National Archives of the Republic of Belarus or the Russian State Military Archives in Moscow.
The Institute of National Remembrance’s archive also has documentation related to the Soviet repression against Polish citizens from the years 1939–1956, collected by Jędrzej Tucholski, a researcher of the Katyn Massacre and a longtime employee of the IPN, as well as materials regarding the Katyn Massacre that the IPN received from the Polish Underground Movement Study Trust in London.
The archival resources of the Institute of National Remembrance in Warsaw contain documents produced by the Red Army, security offices and bodies of the USSR and former Soviet republics - Belarus, Lithuania, Ukraine or Georgia. Among them there are many extremely valuable and interesting documents, including lists of Polish citizens interned in Lithuania, including officers of the State Police and soldiers of the Border Protection Corps, files of criminal investigation cases of Polish citizens (regarding, among others, members of Polish independence organizations operating in the Eastern Borderlands of the Second Polish Republic), reports by the People's Commissariat of Internal Affairs of the USSR, devoted to the activities and liquidation of Polish underground organizations or quantitative lists of rail transports exporting Polish prisoners of war from Kozelsk, Ostashkov and Starobelsk.
One of the most valuable acquisitions in recent years is the documentation and databases of the research programme "Index of the Repressed" run by the KARTA Center in 1988–2013. Pursuant to the agreement signed on 30 April 2013 between the Institute of National
Remembrance and the KARTA Center, the Institute took over the conduct of this programme, dealing with the personal documentation of the fate of Poles and Polish citizens of other nationalities, repressed by the Soviet authorities after 17 September 1939. The archival resource of the Institute in Warsaw then came to include originals of several thousand personal surveys (describing the fate of over 50,000 people) collected during the implementation of the "Index of the Repressed" programme, copies of documents obtained in the archives by the "Memorial" Association in Moscow (a Russian non-governmental organization documenting and disseminating knowledge about the victims of communist political repression), personal questionnaires collected during work on the Books of the Dead prepared by the Siberian Association in Gliwice, as well as numerous copies of name lists from the collections of the Eastern Archives operating at the KARTA Center.