Teenagers spend an incredible amount of time on smartphones, especially on social media and online games. The purpose of this study is to investigate the gender differences and relationship between smartphone, game, social networking sites (SNS) addiction and students' grade point average (GPA) scores. High school students from grades 9-12 (N=504) responded the online survey including different addiction scales. The results indicated a significant correlation between smartphone, SNS, and game addiction however no significant correlation found between students' addiction and GPA scores. Addiction levels between boys and girls also differed significantly. Results of this study have important implications and provide up-to-date example for further research studies in terms of addiction, academic performance and gender differences.