This one-year prospective observational study is designed to evaluate and compare outcomes effectiveness between OROS-MPH and IR MPH in ADHA and ODD symptoms at the ADHD Clinic of the British Columbia Children's and Women's Health Centre. A practical clinical trial is valuable because it has the potential to provide us the information which represents the actual outcomes in real settings.

The primary objective of this study is to analyze the treatment outcomes of ADHD patients under conditions of routine clinical practice. Patients will, therefore, be treated according to the current practice of each participating physician, with the exception of several additional rating scales which are SNAP-IV, Strengths and Difficulties Questionnaire, WEISS Functional Impairment Rating Scale (WFIRS)-Parent, Child Health and Illness Profile (CHIP), EQ-5D, Parent/Caregiver Questionnaire, ADHD Side Effect Checklist, Adolescent Diversion Questionnaire, Adaptive Behavior Assessment System-Second Edition (ABAS-2) and Clinic Global Impressions. Patients will be assessed at baseline and 12 months regardless of whether the original treatment is continued. If a patient terminates the study early, all assessments that are normally collected at the end of the study will be collected at the time of termination. Only patients with pre and post data will be included in the analysis.

Results of this study are expected to make breakthrough on the treatment of ADHD in practice; and, particularly, information which come out from this study is not currently available from other researches.