The article surveys the question how the past of the Grand Duchy of Lithuania and the Commonwealth of Both Nations is used in region’s cross-border issues, and the question could it be the ideological basis for the idea of the Intermarium is raised. The analysis of the countries of the region revealed that these themes in Lithuania, Poland and Belarus are basicaly used for the creation of the identity of the societies, however in any country these topics of the past are not dominating, moreover in Ukraine the theme of the Grand Duchy of Lithuania and the Commonwealth of Both Nations is in marginal position. The central position in the memory culture of these societies take the events of the 20th century. Obviously such secondory position of the understanding of the events of the past showed the commemoration of the anniversary of the Union of Lublin in Poland in 2009. The analysis of the historical research demonstrates different view. Evaluations of the historians in four countries do not differ so cardinally as it was before 1990. Such situation is as a signal that probably it is a time to think about the preparation of the general textbook for schoolchildren of four countries, or synthesis of the history.