In 1940, after the city of Lviv/Lwów had been occupied by the Soviet Union, the Soviet government ordered the seizure of private property. As a result, works from the , integrated with the Ossolineum since 1823, the Borowski Library and several other private collections, are currently in the possession of the gallery. All these works were, until the 1939 Invasion of Poland and subsequent state appropriation, the property of the Polish state, private Polish collectors, and of the Polish Roman Catholic church and, arguably, remain such.