This study would demonstrate the influences of the socio-economic status of citizens, online resources and psychological factors on the three key behaviors of online citizen participation. Focusing on alternative hypotheses in which different empirical grounds were presented, this study investigated if online citizen participation in South Korea would reflect inequality in the traditional citizen participation as it was. As a result of an analysis, using Heckman Selection Model, in spite of the recent survey result that the gap in physical accessibility to digital devices had decreased greatly, it was observed that in the use of the Internet, there were still significant gaps according to age, income level, and education level. However, to examine the characteristics of online citizen participation, focusing on Internet users, there was no great difference according to individual socio-economic status. Rather, it turned out that the positive influences of digital literacy related to information sharing ability and online network level were significant, regardless of the characteristics of each type of participation. Socio-economic background and individual level of interest in society differed depending on the type of participation. For participation in a relatively simple form like “the expression of opinions about public issues, ” no differences were reported by age and by education level, while it turned out that the participation of unemployed people and the people interested in the whole society was relatively more active. For online voting, educational level only was a significant factor affecting that, and it was noted that the higher the educational background, the more active the activity became. However, there were noticeable differences in policy suggestion and proposal activity, which could be said to be a more advanced form of participation according to the socio-economic background. The people with a higher income level and educational background participated more actively. Also, it was reported that men participated more actively than women did. For the gap by age, unlike the general recognition, rather, those in their 30s-60s participated more actively than the younger generation.