The aim of this article is to investigate the phenomenon of cohabitation in Italy through Istat data on the cohabitation trends in the last decades and the results of a qualitative research, based on in-depth interviews among people who cohabited or married after cohabitation, with or without children. The analysis of the interviews shows that the meaning of cohabitation changes according to the experiences of leaving the parental home and the life course stages crossed by interviewees. Marriage is valued for its legal and functional aspects, as a protection of the less financial independent partner. So it becomes a necessity only if the financial condition between partners is unbalanced in order to redress this asymmetry. If the partner conditions are equal - which is the case of the interviewees - marriage does not add benefits. Therefore all social and religious aspects of marriage are excluded by interviewees who were married or plan to marry only for instrumental reasons.