The present study examined individualized behavioral change of externalizing and internalizing problems of adolescents in residential youth care, divided into different change groups (improvement, no change, or deterioration), by using the reliable change index. We also identified demographic and clinical factors that may predict individual behavioral change. A naturalistic dataset was used which consisted of adolescents referred to open or compulsory residential care who had outcome measures at the beginning and end of treatment. In total 742 reports of behavior problems were included: the sample consists of 265 adolescents with self-reports, 341 adolescents with group care worker reports, and 136 adolescents with parent reports. Only 42 adolescents had three sources of report, 202 adolescents had two sources of report, and 212 adolescents had one source of report. The majority of adolescents (50-73%) showed nonsignificant change in either externalizing or internalizing problems during their stay in residential care, regardless of informant. Higher problem severity at the beginning of treatment was a significant predictor of improvement in externalizing and internalizing problems throughout treatment, but the other factors (i.e., age, gender, ethnicity, and treatment duration) showed no effect. In conclusion, this study shows that with the current system of monitoring, more than half of the adolescents in residential care do not show significant change over time. This may indicate either that residential stay does not necessarily cause a significant change in problems for all adolescents, or that the system currently used for treatment monitoring is suboptimal in detecting such a change. (PsycInfo Database Record (c) 2021 APA, all rights reserved).