Background: Because major depression and panic disorder are both more prevalent among females and since several lines of evidence suggest that genetic factors might influence an individual's vulnerability to panic disorder, gene-gender interactions are being examined in such psychiatric disorders and mental traits. A number of studies have suggested that specific genes, e.g. catechol-O-methyltransferase (COMT), might lead to distinct clinical characteristics of panic disorder. Method: We compared gender-specific personality-related psychological factors of 470 individuals with panic disorder and 458 healthy controls in terms of their COMT Val158Met polymorphism and their scores on the Revised NEO Personality Inventory (NEO PI-R) and State-Trait Anxiety Inventory (STAI) with a 1-way analysis of covariance. Results: In the male panic disorder patients, the NEO PI-R score for openness to experience was significantly lower in the Met/Met carrier group, whereas there was no such association among the female panic disorder patients or the male or female control groups. Conclusion: The gender-specific effect of the COMT genotype suggests that the COMT Val/Met genotype may influence a personality trait, openness to experience, in males with panic disorder.