"National treasure" is one of the key notions of cultural heritage law. It is of particular relevance for the European Union in the context of the free movement of goods in the Single Market and the permitted exceptions to this freedom. In principle, it refers to those objects "possessing artistic, historic or archaeological value" whose preservation is in the vital cultural interest of the Member State concerned. Hence national law constraints on their import and export do not violate treaty obligations in force so long as such constraints are not arbitrary or do not constitute disguised restrictions on trade between Member States. The question arises, however, as to the practical meaning of this notion, i.e. whether Member States can freely determine what constitutes a "national treasure". This article seeks to answer that question by analysing how the notion of national treasures was transposed into the Polish legal system in 2017, and what the consequences of this recent regulatory intervention might be.