Objectives: We analyzed a standard children's quality measure for attention-deficit/hyperactivity disorder (ADHD) using data from a single state to understand the characteristics of those meeting the measure, potential barriers to meeting the measure, and how meeting the measure affected outcomes. Study Design: Retrospective study using claims from Alabama's Children's Health Insurance Program from 1999 to 2012. Methods: We calculated the quality measure for ADHD care, as specified within CMS' Child Core Set and with an expanded denominator. We described the eligible population meeting the measure, assessed potential barriers, and measured the association with health expenditures using logit regressions and log-Poisson models. Results: Among those receiving ADHD medication, 11% of enrollees were eligible for annual measure calculation during our study period. Calculated as specified by CMS, 38% of enrollees met the measure. Using an expanded denominator of 7615 eligible medication episodes, 14% met all aspects of the measure. Primary reasons for failing to meet the measure were lacking medication coverage (64%) and lacking a follow-up visit within 30 days (62%). The rate of meeting the measure decreased with age and was lower for black enrollees. Health service utilization and costs were greater among children meeting the measure. Conclusions: Too few children are eligible for inclusion, and systematic differences exist among those who meet the measure. The measure may be sensitive to arbitrary criteria while missing potentially relevant clinical care. Refinements to the measure should be considered to improve generalizability to all children with ADHD and improve clinical relevance. States must consider additional analyses to direct quality improvement.