This study is a four-month, phase IV, open-label study of ADHD symptomatology and functional outcomes in pediatric (6 to 17 years old) and adult (≥18 years or older) patients with ADHD treated with FOQUEST or VYVANSE.

After giving written, informed consent or assent (for patients <18 years old), patients will be screened to ascertain their suitability for the study according to the patient selection criteria (Section 4). Based on clinician assessment, patients will be assigned to receive either FOQUEST or VYVANSE. Patients will be titrated to their optimal dose of ADHD medication based on Investigator judgement. At monthly visits, patients will have their ADHD symptomatology evaluated by the Investigator (ADHD-Rating Scale-DSM 5 Version [ADHD-RS-5]) and will complete questionnaires on functional outcomes (Weiss Functional Impairment Ratings Scale - Parent [WFIRS-P] or Weiss Functional Impairment Ratings Scale - Self [WFIRS-Self]), morning and evening behaviours (Daily Parent Rating of Evening and Morning Behaviours - Revised [DPREMB-R] or Adult ADHD Quality of Life Rating Scale - Revised [AAQoL-R]) and Patient Sleep & Satisfaction survey (PSS). Safety will be evaluated through non-directed spontaneous adverse event (AE) reporting. Patients will be monitored for signs of suicide-related behavior, as per standard of care. A post-study safety follow-up phone call (conducted between 7 and 14 days post-last visit) will assess patients for any adverse events that occur following their last dose of medication received as part of the study. Following the last dose of study medication, the patient's continuing, post-study ADHD treatment will be based on Investigator discretion and standard of care.

Inclusion Criteria:

1. Pediatric: Male or non-pregnant, non-nursing female patients the age of 6 to less than 18. Adults: Male or non-pregnant, non-nursing female patients the age of 18 or older.
2. Diagnosed with ADHD (inattentive, hyperactive or combined-type) who are deemed eligible to receive treatment with FOQUEST or VYVANSE, as per the respective Product Monograph.
3. Mentally and physically competent to provide informed consent, or assent and able and willing to comply with the study protocol, including the study duration.

Exclusion Criteria:

Potential patients who meet any of the contraindications or warnings detailed in the respective Canadian Product Monographs are excluded from participation in the study:

1. Having a true allergy to methylphenidate or amphetamines or sympathomimetic amines, history of serious adverse reactions to methylphenidate or amphetamines or be known to be non-responsive to methylphenidate or amphetamine treatment. Non-response is defined as methylphenidate or amphetamine use at various doses for a phase of at least four weeks at each dose with little or no clinical benefit in the past 10 years.
2. Females of child-bearing potential (FOCP) who are pregnant, planning on becoming pregnant or breast feeding.
3. Having a history of hyperthyroidism, thyrotoxicosis, advanced arteriosclerosis, severe renal insufficiency or glaucoma.
4. Having structural cardiac abnormalities, symptomatic cardiovascular disease or moderate to severe hypertension.
5. Currently, or within the past 14 days, receiving MAO inhibitors.
6. Having a primary diagnosis of bipolar disorder, as assessed at Visit 1.
7. Currently receiving any investigational drug, or have received an investigational drug in the previous month.
8. Having a history of drug or alcohol abuse or dependence.
9. Currently considered a suicide risk by the Investigator.