Randomized, Double-blind Safety and Efficacy Study of Lisdexamfetamine Dimesylate (LDX) in Children and Adolescents Aged 6-17

Inclusion Criteria: 1. Subject is a male or female aged 6-17 years inclusive at the time of consent. 2. Subject must meet Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition - Text Revision (DSM-IV-TR) criteria for a primary diagnosis of ADHD based on a detailed psychiatric evaluation. 3. Subject must have a Baseline ADHD-RS-IV total score ≥28. 4. Subject has blood pressure measurements within the 95th percentile for age, gender, and height at Screening and Baseline. 5. Subject is able to swallow a capsule. Exclusion Criteria: 1. Subject has failed to respond to more than one adequate course (dose and duration) of stimulant therapy. One course must have been a long-acting formulation. 2. Subject has a conduct disorder. Oppositional Defiant Disorder is not exclusionary. 3. Subject is currently considered a suicide risk, has previously made a suicide attempt or has a prior history of, or is currently, demonstrating active suicidal ideation. 4. Subject has glaucoma. 5. Subject weighs less than 22.7kg (50lbs). 6. Subject is significantly overweight based on Centre for Disease Control and Prevention Body Mass Index (BMI)-for-age gender specific charts at Screening. Significantly overweight is defined as a BMI \>97th percentile for this study. 7. Subject has a documented allergy, hypersensitivity, or intolerance to amphetamine or methylphenidate. 8. Subject has a documented allergy, hypersensitivity, or intolerance to any excipients in the test or reference products. 9. Subject has a history of seizures (other than infantile febrile seizures), a tic disorder, or a current diagnosis and/or a known family history of Tourette's Disorder. 10. Subject has a known history of symptomatic cardiovascular disease, advance arteriosclerosis, structural cardiac abnormality, cardiomyopathy, serious heart rhythm abnormalities, coronary artery disease, or other serious cardiac problems that may place them at increased vulnerability to the sympathomimetic effects of a stimulant drug. 11. Subject has a known family history of sudden cardiac death or ventricular arrhythmia. 12. Subject is well controlled on their current ADHD medication with acceptable tolerability. 13. Subject has a pre-existing severe gastrointestinal tract narrowing (pathologic or iatrogenic).