The article discusses the complicated situation of post-German cultural property held within Poland’s borders after the Second World War. On 2 August 1945, ‘the Big Three’ decided a new layout of power within Europe. They reached an agreement that Silesia, Pomerania, the Free City of Danzig (Gdańsk), and part of East Prussia (Regained Territories) along with all the property which had been left on site, should be a part of Poland. One of the post-war priorities of the Polish Government was to regulate the legal status of post-German cultural property left within these newly-delineated borders. Although the Second World War ended in 1945, there was still a threat that the majority of post-German property could be devastated, destroyed, or even looted. There are some documented cases where such cultural property was seized inter alia by the Red Army and then transported to Russia. Since 1945, Russian museums have exhibited many of these pieces of art. This article addresses the question concerning the legal status of post-German cultural property in light of public international law. Furthermore, the article responds to the question, whether Poland is entitled to restitution of post-German cultural property looted from the Regained Territories.