EN
Social research shows that family is still one of the most important value of life for Poles. At the same time we can observe that social definition of family is changing. There are many factors that influence changes in definition of family. Major influential factor is the emergence of alternative forms of family living, including cohabitation. The main issue of this article is phenomenon of cohabitation in Poland in the context of changes in definition of the family. The focus of this paper is also on definition of cohabitation, scale of cohabitation and public opinion on cohabitation.