This paper presents the results of research on children’s risk of being placed in out-of-home care. The purpose is: firstly, to compare children placed in out-of-home care with non-placed children, secondly, to estimate the children’s risk of entry into care and finally, to compare the results of this study with the results from similar studies. The study is based on register data from the Statistics Denmark. The sample includes all children with Danish citizenship who were born 1981–2003. In order to estimate the risk of being placed in out-of-home care, we use information about the child, the mother and the father. We discovered that especially children who had a mother on disability pension, children who came from broken homes but also children whose mothers were unemployed or receiving social assistance and children whose mothers had a conviction had a high risk of being placed in care. The mother’s characteristics are more important risk factors than the corresponding risk factors of the father. The results, the applied method and the epidemiological inspired analysis make an opportunity to discuss the central concepts and methods of calculation of statistical association, risk, prediction and causal inference in applied sociology and social work.