As a new medium of learning readily connected with the outside world, the Internet has brought unprecedented opportunities to students on the one hand, while becoming a major concern for parents on the other. For parents and educators alike, it is thus critical to stipulate whether and how Internet use is linked to academic achievement. Using panel survey data from middle-school students in northern Taiwan (N = 1,409), this study examines how patterns of Internet use in the 8th grade affect students' performance on their high school entrance exam a year later. The findings confirm that online searching for information helps boost exam scores, while using the Internet for socializing and gaming, as well as going to Internet Cafés, contributes to poorer exam performance. Male and female students differ not only in their patterns of Internet use, but in how these patterns affect their academic performance. While information searching helps both boys and girls, online socializing makes girls particularly vulnerable, and online gaming and Internet Cafés hurt only boys' academic achievement.