Youth within the child welfare system (CWS) have often experienced adverse life events, and many need support from health services. This study aimed to compare mental health problems and health service use among adolescents receiving in-home services (IHS), living in foster care (FC) and general population youth (GP). Data stem from the youth@hordaland survey, a population-based study of adolescents (N = 10,257, age 16-19) conducted in 2012 in Hordaland County, Norway. The adolescents provided self-reported data on CWS contact, health service use, adverse life events and multiple instruments assessing mental health problems. The IHS and FC groups had significantly higher symptom scores across most mental health measures than peers from the GP. Youth receiving IHS had significantly higher scores on measures of general internalizing and externalizing problems, attention deficit hyperactivity disorder (ADHD) and depression compared with peers in FC. Those receiving IHS reported the highest health service use. Adverse life events accounted for a substantial part of the differences between the groups. Mental health problems are frequent among older adolescents within the CWS, especially among youth receiving IHS. Service providers and policymakers should be aware of the present and likely continued challenges faced by many of these youth.adolescence, adverse life events, child welfare, health services, mental health, youth | BACKGROUNDChildren exposed to poverty, inadequate parenting or maltreatment are at risk of mental health problems (