The aim of this dissertation is to investigate the incidence of instability in out-of-home care for children and how children experience this instability. The dissertation consists of two studies. The quantitative study is based on an examination of social work case files of 213 children who began 317 placements in 2005 and 2006. Every placement was followed for a maximum of two years. The qualitative study used interpretive phenomenology as method and is based on interviews with 12 purposively selected children who had experienced placement breakdown at some point during 2011 or 2012.   The quantitative study shows that the majority of children had experienced problems in their home environments prior to placement. Most commonly reported was parents’ substance abuse or mental health problems. Preschool and schoolchildren were more often placed in care due to neglect whereas adolescents were placed because of their own behavior problems or relational problems. Children in the qualitative study described that the problems they experienced prior to coming into care continued to influence them during their time in care. The quantitative study indicates that different types of instability are associated with children’s ages. That is, breakdown was most common for adolescents whereas preschool children more often experienced planned placements changes. Children in the qualitative study gave similar descriptions of planned placement changes and placement breakdown. The difficulty with which these children experienced the move from a foster family or group home depended on their relationship to caregivers. Therefore, planned placement changes from foster homes or institutional settings in which children reported being happy were described as more difficult than breakdown in placements from which children wanted to move. In children’s views, breakdown was caused by mismatches between them and caregivers, mistreatment in care settings, and their own behavior problems. However, children explained that when social workers did not listen to them, behavior problems in the form of running away, self-harming or behaving badly, were the only way of ending placements in which they were miserable. All children in the qualitative study described a wish for close relationships with consistent adults and an opportunity to feel that they belong somewhere. These fundamental needs were difficult for them to have satisfied due to their parents’ problematic life histories, instability in care which repeatedly placed children in new care situations, and a lack of continuity of social workers.