OBJECTIVE: The purpose of this research was to evaluate the reliability and discriminant validity of a behavioral task of impulsivity, the delay-discounting task. METHOD: Young adults were asked to report ADHD diagnostic status and to complete the delay-discounting task. The internal consistency of the task was determined, task performances of individuals with and without self-reported ADHD were compared, and the ability of this task to discriminate between participants with and without self-reported ADHD was assessed. RESULTS: The delay-discounting task showed very good to excellent internal consistency. Furthermore, participants with self-reported ADHD responded to the task in a more impulsive manner than did non-ADHD participants. Finally, moderate discriminant validity for detecting self-reported ADHD using this task was found. CONCLUSION: Findings showed that the delay-discounting task is a promising task for both clinical research and practice as it has strong reliability overall and has moderate discriminant ability for self-reported ADHD in young adults.