Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent mental disorders of childhood and has been a major focus of scientific attention in the past few decades. A wide range of empirical data support the validity of the disorder, its associated burden, and its worldwide distribution. However, uncertainties remain about the rate of treatment around the world. In the United States, it is estimated that approximately 56% of children with a reported diagnosis of ADHD have been treated with medication. The rate of treatment in developing countries is expected to be much lower than in developed countries due to inadequate health care systems, lack of human resources, and poor knowledge of the population with the disorder.