Attention deficit hyperactivity disorder (ADHD) is associated with elevated levels of substance abuse (SA), but the cognitive linkages involved have been little explored. The present study used the Brown Attention Deficit Disorder Scales, the Six-Way Paragraphs, and the Substance Abuse Subtle Screening Inventory (SASSI) to investigate these relationships. It was shown that the ability to sustain attention is necessary to formulate an understanding of the most important aspects of any given piece of information, and that the diminished ability to sustain attention associated with tendencies toward ADHD impairs this type of cognition. These cognitive tendencies in turn were associated with elevated levels of SA. The results show the importance of understanding the cognitive processes involved in SA and ADHD.