Functional imaging studies have the potential to provide valuable information about the neurobiologic basis of child and adolescent mood disorders and their development into adult mood disorders. This chapter presents the clinical characteristics of these disorders in children and adolescents. It discusses the epidemiology, signs, symptoms, comorbidity, and natural course of pediatric mood disorder. Children with depression often present to pediatricians or general practitioners with vague somatic complaints including headaches, stomach aches, or other physical symptoms for which the physician can find no cause. The diagnosis of a mood disorder is often obscured by the presence of other comorbid psychiatric diagnoses, as well as by general medical disorders. The developmental course of mood disorders suggests a continuum of pathology from childhood to adulthood. The chapter covers neuroimaging studies in adults, including activation studies using neurobehavioral probes, and the few imaging studies performed in children and adolescents.