Objective: The effect of manipulating item positioning on self-reported ADHD symptoms was examined. We assessed whether listing DSM-IV ADHD symptoms serially or interspersed affected (a) the correlation between ADHD symptoms and (b) the rate of symptom endorsement. Method: In Study 1, an undergraduate sample (n = 102) completed a measure that listed DSM-IV ADHD symptoms serially and a measure that interspersed DSM-IV ADHD items among non-ADHD symptoms. In Study 2, a separate undergraduate sample (n = 240) completed a measure that listed DSM-IV ADHD symptoms serially and another ADHD measure that interspersed DSM-IV ADHD items among non-DSM-IV ADHD items. Results: Item positioning did not affect the correlation between symptoms, but did reveal a significant bias in the rate of symptom endorsements. Conclusion: These findings suggest that there is significant variability in ADHD symptom endorsements resulting from item positioning. This effect has implications for clinical assessment and epidemiological research of ADHD among college students. (Contains 2 tables and 3 notes.)