Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable condition that affects a significant number of children and adults worldwide. During the past 30 years, the diagnosis and treatment of ADHD has relied on clinical assessment and empirical experience with stimulant medications. More recently, advances in family genetic studies, molecular genetic studies, preclinical research, radiographic imaging techniques and neuropsychological evaluation have significantly enhanced our understanding of the neurobiology of ADHD. This review highlights the current central role of dopamine in the pathophysiology and treatment of ADHD and implications for future advances in diagnosis and treatment.