Modern marriages are concluded based on much greater freedom in perceiving marriage as a social obligation, autonomy of both partners and – to the largest extent – they form a legalized relationship preconditioned by emotional needs. Similar characteristics are part of cohabitation, with the exception of its formalization in the legal sense. The author of the article strives to bring closer the similarities and differences between cohabitation and marriage without attempting to assess which of these relationships is more valuable. Discussed concepts The author of the article presents and discusses theoretical assumptions, legal regulations and models of cohabitation and marriage. Differences and similarities between marriage and cohabitation were shown. In the opinion of the author of the article, reflections on the superiority of marriage to cohabitation are not justified. Such an evaluation is besides stymied by many factors. One of them is the lack of precise definition of a consensual relationship, what its time frames are, what the issue of parenthood looks like in it, a division of home duties etc.