Divorces or separations classed as "cross-border" (parents of different nationalities or leaving in different Member States) lead to very complicated legal situations, notably regarding the relationship between the parents and the children of these former couples. An in-depth analysis of the national situations has been conducted in 6 Member States (France, Germany, Spain, UK, Sweden and Poland). In order to comprehend the breadth and types of problems connected to a cross-border separation of parents, various series of information has been collected and analysed for each of these Member States: available statistical data, international and European legal frameworks; national legislations and practices essentially linked to parental responsibility. Even though progress has been made thanks to the quoted legal instruments, notably the Regulation Brussels IIa, some difficulties of interpretation and implementation together with some gaps have been identified. Several actions may be recommended to enable cross-border separation in the European Union to be dealt more efficiently, notably in terms of mediation and international judicial cooperation.