Purpose: The purpose of this study was to examine impulsivity and self-efficacy according to Internet addiction in adolescents. Method: Subjects were middle and high school students in Daegu (N=486). Data were collected by a self-rating questionnaire including demographic data, a Korean version of Internet addiction, impulsivity and self-efficacy. Result: Impulsivity and self-efficacy according to Internet addition were significantly different (F=22.909. p<.001). There were significant correlations between Internet addiction and impulsivity (r=.280. p<01), between Internet addiction and self-efficacy(r=-.288. p<.01) and between impulsivity and self-efficacy (r=-.665. p<.01). Conclusion: These results indicate that the more addictive to the Internet the more impulsive and the less self-efficacious. Therefore, further studies are needed to generalize these results and examine the effects of Internet addiction more broadly.