Attention deficit hyperactivity disorder (ADHD) is a common neurodevelopmental disorder with a childhood onset of symptoms and impairment. Although it is most frequently identified during elementary school years, epidemiologic data suggest that the onset of ADHD frequently occurs earlier, with presentation as young as 3 years of age. Early identification, however, allows consideration of appropriate interventions. Many data are available on safe and efficacious treatment options for school-aged children who have ADHD; however, little is known about the use of these modalities in preschoolers and, ultimately, the long-term effects of early treatment. Recognition of the preschool presentation of ADHD, appropriate differential diagnosis, and identification of comorbid conditions, and a developmental perspective on the course and potential outcomes of the disorder may guide treatment planning. Newly available data on the safety and efficacy of pharmacotherapy and psychosocial intervention for preschoolers who have ADHD may help clinicians make treatment decisions for these young children and their families.