OBJECTIVES: : Approved treatments in Canada for attention-deficit/hyperactivity disorder (ADHD) include three classes of drugs: short-acting (SA) and long-acting (LA) stimulants and a LA nonstimulant medication. Since ADHD is a chronic condition requiring continuing treatment, compliance to the treatment regimen is important. The objectives of this study were to estimate adherence and persistence to ADHD treatments. METHODS: : A retrospective prescription claims analysis of a random sample of 15,838 ADHD patients from the Quebec provincial health plan (RAMQ) database was conducted. Patients with ≥1 physician claim with a diagnosis of ADHD and a drug claim for a treatment approved for ADHD from July 2004 to June 2009 were considered. Only those patients with no prescription claim in the 3 months prior to the index date (date of first prescription fill) were eligible for inclusion in the analysis. Treatment compliance was estimated using medication possession ratio over a one-year period. Patients were considered nonpersistent if they had not used the ADHD medication for a period of at least 3 months. Proportion of patients who were persistent was estimated at 3, 6, and 12 months after index prescription. RESULTS: : The mean age of the study sample was 14.0 years (SD = 8) and 72.6% were males. The proportion of patients who were ≥80% compliant on SA stimulants (39.4%) was lower compared with LA stimulants (63%, p<0.001) and LA nonstimulants (60.2%, p<0.001). The proportion of patients who were persistent on LA stimulants (81.1%) at 12 months was higher when compared with those on LA nonstimulants (61.7%; p<0.001) and SA stimulants (59.6%; p<0.001). Similar trends were observed at all time points examined.CONCLUSIONS: : Results of these prescription claims analyses indicate that adherence to ADHD treatments is poor, however improved adherence and persistence are observed with LA stimulant formulations. Supported by funding from Shire Development Inc.