The purpose of this study was to determine the gender differences in the relationships between knowledge of, attachment with, and attitude toward a parent brand and perceived risk of, attitude toward, and purchase intension of an extended product in the case of brand extension. A total of 300 survey questionnaires were distributed to 150 male and 150 female college students, and 275 responses were used for the final analysis. The results showed that for male college students, knowledge of the parent brand had a positive relationship with brand attachment with the parent brand, which in turn had a positive relationship with brand attitude toward the parent brand. Knowledge of the parent brand had a negative relationship with perceived risk of the extended product, which again had a negative relationship with attitude toward the extended product. In addition, for male college students, knowledge of the parent brand had a positive relationship with attitude toward the extended product, which also had a positive relationship with purchase intension of the extended product. For female college students, brand attachment with the parent brand had a positive relationship with brand attitude toward the parent brand, which also had a positive relationship with attitude toward the extended product. Brand attachment with the parent brand showed a negative relationship with perceived risk of the extended product, which also had a negative relationship with attitude toward the extended product.