This is a multicenter, multiple dose, randomized, double-blind, placebo-controlled, forced titration study. Patients will be randomized to 1 of 4 treatment groups in a 1:1:1:1 ratio. One-hundred twenty (120) patients are planned to be randomized. Each patient will receive AR08 (0.5, 1, or 2 mg per day) or matching placebo for seven (7) weeks.

Inclusion Criteria:

1. Meets DSM-IV-TR criteria for a primary diagnosis of ADHD based on structured clinical interview, MINI-KID, as assessed by the Investigator
2. Minimum score of 28 on the ADHD-RS-IV at Baseline
3. Male or female ages 6 - 17 years, inclusive, at the time of Screening
4. Weighs ≥21 kg (46 pounds).
5. Is functioning at age appropriate levels intellectually, as deemed by the Investigator.

Exclusion Criteria:

1. Has a comorbid psychiatric diagnosis (comorbid psychiatric diagnosis will be established by the MINI-KID interview).
2. Has a positive response to either question 4 or 5 of the Baseline /Screening version of the pediatric Columbia Suicide Severity Rating Scale (C-SSRS)
3. History of daily usage (at least 28 days/month) of either anti-hypertensive or prophylactic anti-migraine medications prior to Screening
4. Current usage of medications known to cause QTc prolongation or ADHD medications.