OBJECTIVES: Approved treatments for attention-deficit/hyperactivity disorder (ADHD) in Canada comprise short-acting (SA) and long-acting (LA) stimulants and a LA nonstimulant medication. The objective of this study was to elucidate different drug treatment patterns to treat ADHD in Canada. 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. Any patient with ≥1 physician claim with an ADHD diagnosis and a claim for a treatment approved for ADHD from July 2004 to June 2009 was considered. RESULTS: The mean age of the study sample was 14.0 years (SD = 8); 72.6% of the sample were males. There were a total of 416,646 ADHD prescriptions during the 5-year study period. As a proportion of total prescriptions, use of SA medications declined from 72.83% in 2004 to 26.38% in 2009, while use of stimulant and nonstimulant LA medications increased from 27.17% to 73.62% over the same period. Approximately half of the patients used both SA and LA medications either concomitantly or subsequently while approximately 30% used only SA and 19% used only LA. Among those patients who used both types of formulations, switching from SA to LA was the most frequent (27.9%) treatment pattern. A greater proportion of patients (6.4%) on LA methylphenidates required augmentation with SA medications when compared with those on LA amphetamines (1.9%; p<0.01)CONCLUSIONS: : Results of this RAMQ database analysis illustrate that over time, patients shifted from the use of SA stimulants to formulations that provide all-day coverage. Switching from SA to LA medications and augmentation of LA medications with SA medication are common treatment patterns observed in the management of ADHD with implications for patient care and the efficient use of health care resources.  Supported by funding from Shire Development Inc.