The abuse of the internet creates the problem of ′Internet Addiction′ in the lives of college students. The purpose of this study is to investigate the characteristics and effects of ′Internet Addiction′ in college students. Data was gathered by in-depth interviews with 13 college students who use the internet addictively. The internet addictive group was divided into three subtypes:internet game addicts, personal relation addicts and majors in computer science. There were many characteristic differences among the internet addict subtypes in internet use, and psycho-social traits, such as self-efficacy, impulsiveness, and time management ability. The effects of "Internet Addiction" in the lives of college students were divided into five categories: emotional problems, physical problems, family relationship problems, friendship problems, and schoolwork problems. This study suggests some implications on developing programs for managing and schoolwork problems. This study suggests some implications on developing programs for managing and preventing "Internet Addiction."