The Personality Assessment Inventory (PAI) is a widely used and available self-report measure designed to assess clinical syndromes and has the potential to assist in the process of ADHD assessment. Since the PAI's inception, several researchers have attempted to create other supplemental indicators, some so effective and useful that they were added to the second edition of the Personality Assessment Inventory Professional Manual. Previous researchers have offered important insights into the possibility of the creation of an ADHD item-level index for the PAI that would effectively decrease false positive rates and increase accurate detection of ADHD in the adult population. Previous researchers were not successful in creating an item-level subscale that reliably detected adult ADHD. Four experts in ADHD assessment rated PAI items that they believed could discriminate adults with ADHD from adults without ADHD. After performing a PCA on the top 16 items chosen by the experts, 12 items sufficiently loaded onto one factor that has clear face validity by conceptually matching the DSM-5 description of inattention and impulsivity commonly seen in adults with ADHD as well as the "internalized restlessness" Hallowell and Ratey describe for adult ADHD. The PAI-ADHD was found to have good internal consistency, a = .84. The PAI-ADHD has good convergent validity with the Conners' Adult ADHD Rating Scale – Self-Report – Long Version (CAARS-Self) and Wender Utah Rating Scale (WURS). The PAI-ADHD also has good concurrent validity. Two cut scores are suggested, 13 and 22, to maximize sensitivity (.88) and specificity (.89), create three screening groups: ruled-out, at-risk, and probable ADHD, and increase utility for clinicians.