The contemporary management of the adolescent patient on the psychiatric inpatient adolescent unit in the twenty-first century entails a new type of comprehensive and wide ranging familiarity with several types of clinically challenging co-occurring disorders including cannabis use disorder and eating disorders. In this article, there is a delineation of current understanding of the prevalence of these diagnoses in addition to a review of prevailing expert opinion as to principles of evaluation and management of these conditions in patients stabilized on the adolescent inpatient psychiatric unit.