The article aims to present the trends in cultural heritagisation of artworks of the synthesis of the arts, a prominent phenomenon of Lithuanian architecture of the second half of the twentieth century. In post-war Lithuania, synthesis of arts was encouraged: as it enabled the development of the branches of monumental and applied art, it was generally accepted that the surviving artworks of these branches were of historical and iconographic value. Nevertheless, these works could also be linked to the social engineering programme of the occupying Soviet government. The article evaluates the origins of the idea of the synthesis of the arts and its adaptation in the Soviet Union, which provides an understanding of both the ways in which the idea of the synthesis of the arts was used for propaganda purposes and the motivation of the creators of monumental and applied art that transcended the boundaries of propaganda. The analysis of the sources carried out in the article allows grasping the shift in the concept of the synthesis of the arts that took place in post-war Lithuania, which created the conditions for the manifestation of the personal character of art, the innovativeness of the expression, and conditional political neutrality. For the first time, the analysis of the data of the Register of Cultural Property was conducted to reveal that neither the criteria allowing recognition of non-ideological works nor the usual “50 years of age” requirement had a prominent impact on deciding which artworks should be declared cultural heritage in Lithuania. Due to the lack of a consistent value-based strategy and the acceleration of the destruction of the art of the Soviet period, the strategies for the identification and cultural heritagisation of art synthesis artworks are sporadic and inconsistent. The analysis carried out in the article demonstrates how uncoordinated efforts to preserve such artworks, lacking in systematic and contextual approach, as well as the contradiction between works created specifically for architecture and their treatment as detachable objects, have a fatal impact on their actual (not formal) preservation.