Closing the gap between evidence-based clinical practice standards and their inclusion in routine practice continues to be a major goal of health policy reforms. This gap is especially large for the care of children with psychiatric disorders-especially those from low-income families, many of whom are insured through Medicaid. To address this gap, we analyzed trends over ten years (2001-10) from Medicaid claims data describing changes over time in medication, psychotherapy, and combined treatment services for children diagnosed with attention deficit hyperactivity disorder (ADHD). Over this time, more children received treatments that conformed to practice standards, including the use of combination treatments of medication and psychotherapy. Rates of combined treatment increased by 74 percent, rates of psychotherapy alone more than doubled, and rates of medication alone decreased by 18 percent. Rates of diagnoses without any reimbursed treatment decreased by 39 percent. These trends suggest increasing adherence to clinical practice standards by providers serving children with ADHD in the Medicaid population, although the quality of those services is unknown.