This chapter covers two distinct domains of disorders: substance use/abuse and impulse control disorders. Although these are distinct problems, the concepts are linked by a common thread of inhibitory control. These issues are not usually the reason for referral of a patient for neuropsychological evaluation, but they may be encountered in history of the individual. An understanding of the nature of the substances, disorders, their neuroanatomy, and the neuropsychological findings associated with them may be helpful in considering the impact of these issues on a person's neuropsychological functioning.