OBJECTIVES: To characterize changes in the demographic distribution of attention-deficit hyperactivity disorder (ADHD) diagnosis from 2004 to 2012 in the United States. METHODS: ADHD diagnosis data was extracted from the National Health and Nutrition Examination Survey (NHANES) Summary Health Statistics for U.S. Children, a source of nationally representative data on children in the United States. The ADHD cases were identified based on ICD9-CM diagnosis codes. Chi square tests were used to investigate differences in ADHD diagnosis rates by demographic characteristics (age, race, and gender) within each year and simple linear regression was applied to determine the extent of change over time. All statistical analyses were performed using SAS 9.2 (SAS Institute, Cary,NC) at a priori significance level of 0.05. RESULTS: The ADHD diagnosis rate was higher among males, Whites, and school aged children and adolescents (vs. preschoolers aged 3-4) in each year examined. The total number of ADHD cases as well as all demographic groups with the exception of African Americans and preschoolers aged 3-4 exhibited an increasing trend between 2004 and 2012. CONCLUSIONS: ADHD diagnosis among youth showed a significant increase in the U.S. between 2004 and 2012. Notable increases and group differences were also observed among demographic subgroups. These findings indicate a need for future research in reasons for such group differences as well as treatment differences.