This is an in-depth, cross-national comparative study of living arrangements of young people in Europe. It compares France and Spain and proposes a theoretical framework for understanding international variations in young people's living conditions and transitions to adulthood. The study attempts to answer the question: Why do some young people stay longer at home than others? This leads to a sociological interpretation of differences in the opportunity structure of young people and of their respective strategies in the transition to social independence. This research links micro and macro-level analysis and matches two national large-scale surveys to treat a topic which is of relevance to many people, especially with regards to social policy reforms.