Objective: Higher rates of conflict are observed between adolescents with ADHD and their parents due to cognitive, academic, social, and behavioral difficulties. Conflict should be even more pronounced when parents have ADHD themselves; however, some research suggests that parents with ADHD may have increased tolerance toward children who share similar challenges (i.e., similarity-fit hypothesis). Method: We tested the similarity-fit model and its converse, the similarity-misfit model, in a sample of 93 ADHD adolescents, 63 comparison adolescents, and their parents with varying levels of ADHD. Quantity and intensity of conflict were examined in mothers and fathers separately. Results: We found evidence for the similarity-fit process in fathers, and similarity misfit in mothers, particularly regarding quantity of conflict between parent and adolescent. Conclusion: Results indicate the importance of differential parental roles in mothers and fathers, and have implications for involving parents in treatment for ADHD in adolescents.