Incarcerated juveniles are a unique, understudied, and highly vulnerable patient population. Mental and substance-related disorders are significant public health problems affecting youth in juvenile justice and adult correctional settings. Comorbidity is the norm, rather than the exception. A newly detained youth might have (1) a past diagnosis of attention-deficit/hyperactivity disorder, a learning disorder, or oppositional defiant disorder, (2) school-based altercations, suspensions, or expulsions, (3) worsening disruptive behaviors at home and/or in the community, (4) recent police or legal involvements, (5) other high-risk behaviors, (6) recent alcohol, nicotine, or cannabis abuse, or (7) myriad other acute or chronic medical conditions. Compliance with recommended outpatient medical or mental health treatment is typically highly variable. Many of these youths have a history of mental health treatment, with or without psychotropic medication treatment.