The CAT-A is a 108-item self-report instrument that is comprehensive, highly reliable, and sensitive to the symptomatology of attentional deficits both with and without hyperactivity for adults. Closely aligned with current diagnostic criteria, the CAT-A includes scales, clusters, and items that are sensitive to symptom presentation in differing contexts and as expressed as either internal sensations or overt behaviours. The CAT-A consists of two parts: Part 1 (Childhood Memories) assesses the individual’s memories of his/her behaviours and sensations as a child, and Part 2 (Current Symptoms) assesses parallel issues in adulthood. The CAT-A provides Clinical Index scores for the Childhood Memories section, the Current Symptoms section, as well as the summation of these two sections. In addition, three validity scales are embedded within the instrument–Negative Impression, Infrequency, and Positive Impression.