Background Children and adolescents in child welfare are characterised by a high rate of psychopathology. However, prevalence estimates vary greatly, and comparisons between studies are limited owing to different target populations, measurement tools and how results are presented. In addition, little is known about the situation of children under child welfare care still living with their parents. Methods The Achenbach System of Empirically Based Assessment and the Strengths and Difficulties Questionnaire used to measure psychopathology, were administered to parent, agency carer and adolescent (if older than 11). Data of 292 children aged 3–17 years (mean age, 12.13 years) with at least one respondent of four types of placement, namely foster care, residential care, day care and home-based care, were included (response rate, 78%). Socioeconomic characteristics and psychopathology were examined across these four types of placement. Results Overall, the proportion of children scoring within the clinical range according to at least one informant was 56% according to the Strengths and Difficulties Questionnaire and 54% according to the Achenbach System of Empirically Based Assessment. Rates were highest among children living at home and significantly lower among children in out-of-home placement, even after correcting for age, income and duration of the ongoing placement. Adolescents scored themselves lower on psychopathology in comparison with their parents and the agency carer. Conclusions The prevalence of psychopathology in this child welfare population was very high; however, the findings were consistent with results obtained in previous studies. The prevalence estimates differed depending on the type of placement: the highest rates were found among children in home-based care, and children in foster care suffered less psychopathology. The findings stress the vulnerable mental status of children in child welfare and the need for additional support for child welfare professionals and ...