Depression in childhood and adolescence is a chronic, recurring, and highly morbid disorder associated with poor psychosocial functioning, suffering, and attempted and completed suicide. This chapter throws light on how to diagnose depression in children and adolescents. It explores how the clinical picture of depression changes between childhood and adulthood, and focuses on ways people can adapt interviewing techniques for children. The information that the parent conveys helps to structure the interview with the child and helps efficiently and completely to elicit symptoms from the child. Reliability on the Schedule for Affective Disorders and Schizophrenia for School-Aged Children (K-SADS) and other instruments suggests that the diagnosis of depression in children and adolescents could be made as reliably as these diagnoses are made in adults. Discussing psychopharmacologic treatment, the chapter highlights that for medication, a selective serotonin reuptake inhibitor (SSRI) is most likely the first choice.