Objective: The purpose of this study was to use hierarchical linear cluster analysis to examine the normative personality styles of adults with ADHD. Method: A total of 311 adults with ADHD completed the Millon Index of Personality Styles, which consists of 24 scales assessing motivating aims, cognitive modes, and interpersonal behaviors. Results: The sample was randomly divided into half, and independent hierarchical linear cluster analyses were performed on each half to identify replicable clusters. A three-cluster solution was selected, and two of the clusters were replicated across the independent analyses. Participants in Cluster 1 manifested more polarized, negative motivating aims, cognitive modes, and interpersonal behaviors than participants in Cluster two. Conclusion: Hierarchical linear cluster analyses identified two very different personality styles in a sample of adults with ADHD, with implications for clinicians and future research. (Contains 3 figures and 1 table.)