This research investigated the impacts of gender and sensation seeking on predicting the causes of problematic Internet use by high school students. This study’s sample group included 458 students (262 girls and 196 boys) studying at Anatolian High Schools located in the Konak district of Izmir city. Participants filled out self-evaluation documents incorporating the Scale for Internet Use by Adolescents, the Zuckerman Sensation-Seeking Scale, and personal data forms. Hierarchical regression was used for data analysis, and the findings revealed that sensation seeking and gender accounted for 47% of the variance related to Internet addiction. Examination of these results indicated that the most powerful variable leading to problematic Internet use was the pursuit of new experience under the sub-dimension of thrill seeking, followed successively by boredom susceptibility, gender, thrill and adventure seeking, and disinhibition. Even though this research contributes to previous studies on the role of gender and sensation seeking in problematic Internet use, more research is needed on this subject.