Cannabis use may impair cognitive functions on a number of levels—from basic motor coordination to more complex executive function tasks, such as the ability to plan, organize, solve problems, make decisions, remember, and control emotions and behavior. These deficits differ in severity depending on the quantity, recency, age of onset, and duration of marijuana use. Understanding how cannabis use impairs executive function is important for clinicians. Individuals with cannabis-related impairment in executive functions have been found to have trouble learning and applying the skills required for successful recovery, putting them at increased risk for relapse to cannabis use. Here, we review the research on the acute, residual, and long-term effects of cannabis use on executive functions and discuss the implications for treatment.