Excess body weight has been shown to increase the risk for development of several common cancers, such as postmenopausal breast, colon, endometrium, kidney, and esophagus cancers. The main aim of the present study was to investigate the potential relationship between excess body weight, assessed in terms of BMI, and Breslow thickness in 605 patients affected by primary cutaneous melanoma. Particularly, we evaluated the occurrence of thick melanoma (>1 mm) in overweight compared with nonoverweight patients. The effect of BMI (≥25 vs. <25 kg/m2) on the risk of having a diagnosis of thick melanoma was estimated in terms of odds ratio (OR) by logistic regression analysis, adjusted for age, sex, and histological type. Significant differences in overweight versus nonoverweight patients were found with respect to sex distribution. In fact, the occurrence of thick melanoma was greater in overweight women than in nonoverweight women (OR=1.64). When the analysis was restricted to postmenopausal women, the corresponding OR increased further to 2.50. In conclusion, a positive association between excess body weight and the risk of thick melanoma was found only in female patients. On stratifying patients into subgroups, the relationship between the risk of being diagnosed with a thick melanoma (>1.0 mm) and overweight status (BMI≥25 kg/m2) was significantly affected by both sex and menopausal status. Despite limitations because of both the study design and the relatively small numbers of patients in certain subgroups, overweight status may be associated with an increased Breslow thickness in postmenopausal women.