The «new museology» movement, which seeks to revise the principles and foundations of the activities of modern museums, has introduced a few new concepts into consideration, one of which is the concept of «social object». «New Museology» interprets a social object as the basis for constructing an exposition of a participatory museum, which makes it possible to consider a social object as an analogue of a museum item. Since the concept of a «museum item» is one of the key theoretical tools of modern museology, its content can be expanded within the framework of the scientific understanding of a participatory museum. Directions of such a theoretical study are presented in this article. The analysis of the transformation of a museum object into a social object during the transition from the traditional principle of building a museum exposition to a participatory one made it possible to identify several problems in the activities of a participatory museum related to the communication potential of its exhibits. The understanding of a social object is formed based on an analysis of examples of exposition and exhibition activities presented in the book by N. Simon «The Participatory Museum».