Objective: To identify children with ADHD enrolled in New York State (NYS) Medicaid and characterize ADHD-associated costs by treatment category. Method: In 2013, 1.4 million children aged 2 to 17 years were enrolled in NYS Medicaid. Medicaid claims and encounters were used to identify children with ADHD, classify them by type of treatment received, and estimate associated costs. Results: The ADHD cohort comprised 5.4% of all Medicaid-enrolled children, with 35.0% receiving medication only, 16.2% receiving psychological services only, 42.2% receiving both, and 6.6% receiving neither. The total costs for the ADHD cohort (US$729.3 million) accounted for 18.1% of the total costs for children enrolled in NYS Medicaid. Conclusion: This study underscores the importance of achieving a better understanding of children with ADHD enrolled in NYS Medicaid. A framework to categorize children with ADHD based on their treatment categories may help to target interventions to improve the quality of care and reduce costs.