Introducing the main theme of the issue, the paper is trying to abandon commonplaces and clichés and to emphasize the subjects that were not in focus in earlier research. The papers of this volume show local complexities in how religious factor played in the history of Eastern Europe in the twentieth century. The thesis that some confessions are more engaged in the nation-building than others, seems to be a simplification, because Catholics, Orthodox and Protestants were equally involved in the process of constructing national identity.