This study investigated whether children/youth in Ontario triaged to residential services showed a higher intensity of need than those referred to outpatient services, and whether residential treatment gains were sufficient for transition to community services. Participants included 2,053 children/youth assessed at 23 diverse mental health agencies across Ontario using the interRAITM Child and Youth Mental Health (ChYMH) instrument. Various presenting problems were examined utilizing scales including: Disruptive/Aggressive Behaviour, Hyperactive/Distraction, Social Disengagement, Anxiety, and Sleep Difficulties. Analyses were conducted separately for boys and girls. Notable differences were found in the initial assessment, with residential boys scoring higher on all scales than outpatient boys, and residential girls scoring higher on the externalizing scales (Disruptive/Aggressive Behaviour, Hyperactive/Distraction) than outpatient girls. Treatment gains at residential discharge included improvements in Anxiety, Social Disengagement, Hyperactive/Distraction, and Sleep Difficulties for boys and girls to levels at or below the initial scores of outpatient peers. Disruptive/Aggressive Behaviour is still a high need following residential services. The results highlight differences in severity of mental health presentation between children/youth receiving residential and outpatient services, and how multiple agencies in Ontario are providing services that successfully reduce the severity of mental health needs.