About 20,000 out of about 51,000 Polish POWS died in Soviet and Lithuanian camps Similar number of Soviet POWs - from 16,000 to 20,000 out of 80,000 - perished due to disease and poor conditions in Polish camps in that period.
While the conditions for Soviet prisoners were clearly exposed by the free press in Poland, no corresponding fact-finding about Soviet camps for Polish POWs could be expected from tightly controlled Soviet press of the time. Available data shows many cases of mistreatment of Polish prisoners. There have been also cases of Soviet army executing Polish POWs when no POW facilities were available.
While majority of Polish POWs were held by the Soviet Union, several thousands were held by the government of Lithuania; from soldiers captured during the Polish-Lithuanian War, Żeligowski's Uprising or interned during the Polish-Soviet War. Cases of mistreatment of Polish POWs in Lithuania were frequent and similar to situation in Soviet camps.