PurposeThe purpose of the study was to describe inpatient hospitalization patterns among detained and nondetained youth in a large, total population of hospitalized adolescents in California.MethodsWe examined the unmasked California Office of Statewide Health Planning and Development Patient Discharge Dataset from 1997 to 2011. We considered hospitalized youth aged 11–18 years “detained” if admitted to California hospitals from detention, transferred from hospital to detention, or both. We compared discharge diagnoses and length of stay between detained youth and their nondetained counterparts in the general population.ResultsThere were 11,367 hospitalizations for detained youth. Hospitalizations differed for detained versus nondetained youth: 63% of all detained youth had a primary diagnosis of mental health disorder (compared with 19.8% of nondetained youth). Detained girls were disproportionately affected, with 74% hospitalized for a primary mental health diagnosis. Detained youth hospitalized for mental health disorder had an increased median length of stay compared with nondetained inpatient youth with mental illness (≥6 days vs. 5 days, respectively). This group difference was heightened in the presence of minority status, public insurance, and concurrent substance abuse. Hospitalized detained youth discharged to chemical dependency treatment facilities had the longest hospital stays (≥43 days).ConclusionsDetained juvenile offenders are hospitalized for very different reasons than the general adolescent population. Mental illness, often with comorbid substance abuse, requiring long inpatient stays, represents the major cause for hospitalization. These findings underscore the urgent need for effective, well-coordinated mental health services for youth before, during, and after detention.