In order for electronic commerce to be successful, it must have a theoretical framework that considers the characteristics of the internet user who are consumers in the cyber space and impacts their purchase intentions. We were able to obtain participations of 316 people, and derived statistics by means of SPSS/PC version 10.0 and Amos 4.0 statistics package. We found that, the higher the degree of skill and the sense of challenge, the level of involvement and perceived service quality increased. And the degree of skill has a negative influence on awareness of perceived risk than the sense of challenge. Perceived service quality, perceived risk and involvement has a influence on purchase intentions.