Major depression and bipolar disorder in children and adolescents are serious conditions associated with considerable morbidity as well as increased risk of suicide. The treatment of depression in young people is currently controversial and this article reviews the evidence base and potential risks and benefits of antidepressants. Although the diagnosis of bipolar disorder is also controversial, medication is the first-line treatment of choice in cases that meet diagnostic criteria. The limited evidence base in children and adolescents is presented, along with current treatment guidelines. Despite the controversies in this field, this article concludes that medication remains an important part of the treatment approach for both disorders, although the risks and benefits of pharmacotherapy need to be carefully assessed in each patient.