In 2009, Blue Cross-Blue Shield of Massachusetts (BCBSMA) implemented the alternative quality contract (AQC), which pays provider organizations a global payment for all services used by enrollees. BCBSMA claims for 2006-2011 were used to compare youths enrolled in provider organizations participating in the AQC (7,407 person-years [PYs]) with those not participating (45,398 PYs). Difference-in-differences models estimated changes in mental health and substance abuse treatment service utilization and spending attributable to the AQC. The AQC was associated with small increases in the probability of any outpatient visits and in the probability and number of medication management visits among children with attention-deficit hyperactivity disorder (ADHD). Spending did not change, and there was no evidence of reductions in service utilization or spending for children with ADHD in the first three years of AQC implementation.