Although Internet addiction is still under research, individual and social variables play an important role in determining the level of Internet addiction. The aim of this research was to examine the connection between Internet addiction, loneliness, social support and peer pressure in high school students. A total of 105 students from 1st to 4th grade took part in the research, including 43 high school boys, 59 high school girls and 3 people who did not choose their gender, from gymnasium and vocational schools, including economists, CNC operators and trade school. Students filled out the questionnaire via a web survey during teacher's class. Internet addiction is significantly positively correlated to loneliness and peer pressure, and negatively correlated to social support. The results show that high school students who show a higher level of Internet addiction also show a higher level of social and emotional loneliness. Also, high school students who show a higher degree of Internet addiction also show a higher level of perceived pressure to conform to the peer group. In addition, high school students who show lower levels of Internet addiction report higher levels of support from family, friends, and significant others. Lastly, peer pressure, especially loneliness and social support, proved to be significantly related to each other. The obtained results can contribute to the education of social workers about the importance of Internet addiction and the development of a comprehensive prevention program as well as the development of a treatment program for Internet addiction among young people. In conclusion, the consequences that this addiction leaves on individuals gives room for continued research, both in social work and in other sciences.