The purpose of this study was to investigate the impulse buying behavior of men and women in their twenties, who have experiences of purchasing on internet shopping malls, when they buy fashion products. The data in this study was statistically analyzed using factor analysis, reliability coefficient, and multiple regression analysis using SPSS 14.0. The findings are as follows. First, factor analysis revealed five factors of impulse buying behavior during the purchase of fashion products on internet shopping malls: affective impulse buying, provocative impulse buying, situational impulse buying, reminder impulse buying, and pure impulse buying. Second, factors of perceived risk when purchasing fashion products on internet shopping malls included product quality, payment, service, and economy. Third, sources of information included personal sources of media for fashion professionals, commercials and sponsorship, and promotion. Fourth, the effect of the perceived risk on impulse buying behavior was investigated and the result showed that the perceived risk had a statistically significant influence on impulse buying behavior. Finally, the effect of the information source on impulse buying behavior was investigated and the results showed that the use of information sources had a statistically significant influence on impulse buying behavior.