Attention-deficit/hyperactivity disorder (ADHD) is a clinically important neuropsychiatric developmental disorder that affects children, adolescents, and adults. The disorder is characterized by core symptoms of inattention, hyperactivity, distractibility, impulsivity, and impaired executive functioning. It is estimated that 2% to 5% of the adult population in the United States has ADHD. Adults with ADHD are at an increased risk for experiencing comorbid psychiatric disorders, including mood disorders, anxiety disorders, and substance use disorders. The authors provide a brief clinical overview of ADHD and the treatment of adults with this disorder.