Based on longitudinal data collected from a random sample panel survey, the present study found that different types of Internet usage are differentially related to social networks. The more social ties people have, the more likely they are to use personal computer (PC) email, and the use of PC email increases social ties. The results also show that the more supportive ties people have, the more they tend to use mobile phone email; however, it does not prove the use of mobile phone email increases supportive ties. However, participation in an online community is not related social networks. These findings suggest that PC email may increase the size of personal social networks, whereas mobile phone email is useful in maintaining existing strong ties which provide social support.