Mental disorders may have severe consequences for individuals across their entire lifespan, especially when they start in childhood. Effective treatments (both psychosocial and pharmacological) exist for the short-term treatment of common mental disorders in young people. These could, at least theoretically, prevent future problems, including recurrence of the disorder, development of comorbidity, or problems in functioning. However, little is known about the actual effects of these treatments in the long run. In the current editorial perspective, we consider the available evidence for the long-term (i.e., ≥2 years) effectiveness and safety of treatments for attention deficit hyperactivity disorder, behavior disorders, and anxiety and depressive disorders for children between 6 and 12 years old. After providing an overview of the literature, we reflect on two key issues, namely, methodological difficulties in establishing long-term treatment effects, and the risk–benefit ratio of treatments for common childhood mental disorders. In addition, we discuss future research possibilities, clinical implications, and other approaches, specifically whole-of-society-actions that could potentially reduce the burden of common childhood mental disorders.