Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that has been recorded in the medical literature for the last 2 centuries under various names. Most research on ADHD has focused on children, but over the past decade there has been an increase in the documented prevalence and incidence of ADHD among adults. Prescription psychostimulants are first-line pharmacologic treatments for ADHD in adults. However, there is concern for misuse and diversion of psychostimulants, and concern that these medications may lead to a new substance use disorder (SUD) diagnosis or precipitate substance-related problems in people with co-occurring SUD and ADHD. Though existing systematic reviews have examined the use of stimulant medications in ADHD, none have focused exclusively on diagnosed SUD.