The purpose of this dissertation was to expand the understanding of youth in psychiatric residential treatment facilities by using psychosocial indicators to develop subgroup profiles. Additionally, differences in treatment outcomes between subgroups and the extent to which within-treatment factors accounted for observed differences in treatment outcomes between subgroups were examined. Data were extracted from the case records of 447 youth who were served in psychiatric residential treatment facilities over a seven year span of time. A latent class analysis was used to identify and describe subgroups. A series of multivariate regression analyses were used to examine group differences in functional impairment at discharge. Next, a path analysis was used to determine if there were differences in average change in functional impairment from admission to discharge between subgroups and to test within treatment factors as potential mediators of group differences. Finally, a logistic regression was used to determine if there were differences between groups in the probability of discharging to a community-based placement or discharging to another congregate care facility. The latent class analysis revealed four distinct subgroups of youth. The analyses of treatment outcomes revealed statistically significant differences in the level of functional impairment at discharge and average change in impairment between groups. Results from the path model of indirect effects supported that within treatment factors accounted for a statistically significant proportion of the observed difference in change between groups. No differences were found in discharge placement outcomes between groups. Implications for future research, practice and policies focused on youth in residential treatment are discussed.