This study investigated the relationship between various intrapersonal factors and the discrepancy between subjective and objective cognitive difficulties in adults with attention-deficit hyperactivity disorder (ADHD). The first aim was to examine these associations in patients with valid cognitive symptom reporting. The next aim was to investigate the same associations in patients with invalid scores on tests of cognitive symptom overreporting. The sample comprised 154 adults who underwent a neuropsychological evaluation for ADHD. Patients were divided into groups based on whether they had valid cognitive symptom reporting and valid test performance (n = 117) or invalid cognitive symptom overreporting but valid test performance (n = 37). Scores from multiple symptom and performance validity tests were used to group patients. Using patients' scores from a cognitive concerns self-report measure and composite index of objective performance tests, we created a subjective-objective discrepancy index to quantify the extent of cognitive concerns that exceeded difficulties on objective testing. Various measures were used to assess intrapersonal factors thought to influence the subjective-objective cognitive discrepancy, including demographics, estimated premorbid intellectual ability, internalizing symptoms, somatic symptoms, and perceived social support. Patients reported greater cognitive difficulties on subjective measures than observed on objective testing. The discrepancy between subjective and objective scores was most strongly associated with internalizing and somatic symptoms. These associations were observed in both validity groups. Subjective cognitive concerns may be more indicative of the extent of internalizing and somatic symptoms than actual cognitive impairment in adults with ADHD, regardless if they have valid scores on cognitive symptom overreporting tests.