Children diagnosed with attention-deficit/hyperactivity disorder (ADHD) often display reduced cortical volume and thickness, as well as changes in cortical folding. However, the impact of ADHD on cortical morphology in young adults remains elusive. This study aimed to characterize cortical thickness, gyrification, and sulcal depth profiles in adults aged 18-26 years old with ADHD. In this cross-sectional study, we employed multiparameter analyses between two groups: an ADHD group of individuals diagnosed with and medicated daily for ADHD (n = 30) and a non-ADHD group with age- and sex-matched individuals free from lifetime ADHD diagnosis (n = 30). The ADHD group exhibited significant cortical thinning in fronto-parieto-temporal regions, including the left superior parietal lobule, bilateral inferior temporal gyrus, and right lateral orbitofrontal gyrus, relative to the non-ADHD group. Greater gyrification and deeper sulcal depth were evident in various fronto-occipital-temporal regions in the ADHD group, although two regions (right postcentral and inferior temporal gyri) displayed shallower sulcal depth compared to the non-ADHD group. These data suggest that ADHD-related disparities persist into young adulthood, with alterations in brain morphology potentially serving as biomarkers for ADHD diagnosis in young adults.