Introduction. In the modern educational environment, the informatization of the learning process changes the process of development and socialization of schoolchildren. The widespread introduction of information technologies has both a constructive and destructive impact on the formation of young people. This actualizes the need to research the inner world of students who are affected by the negative consequences of excessive involvement in the Internet environment to create a modern system of psychological and pedagogical support. The purpose of the study: to study the influence of the characteristics of personal maturity on the formation of problematic Internet use of high school students. Materials and methods. The study of problematic Internet use was conducted using the CIAS test (Chen's Internet Addiction scale, adapted by V. L. Malygin, K. A. Feklisova). To study personal characteristics, such methods were used as: the scale of self-assessment of personal maturity (A.V. Miklyaeva.); the test of resilience (S. Muddy in the adaptation of D. Leontiev); the scale of socialization (California psychological Questionnaire); the modified method of "Who am I" by M. Kuhn, T. McPartland. The sample consisted of 1,031 people (669 girls and 362 boys), aged 14 to 18 years. Methods of mathematical statistics: methods of descriptive statistics, one-factor analysis of variance, regression analysis. The results of the study. Significant differences were revealed in a number of components of personal maturity in adolescents with different levels of involvement in the Internet environment. High school students with normative Internet use have significantly higher academic performance (H=12.35, p=0.0021), personal maturity (H=24.81, p=0.0001), reflexive maturity (H=76.26, p=0.0001), socialization (H=138.43, p=0.0001), self-esteem of the desire to grow up (H=7.25, p=0.0266). Students with problematic Internet use significantly more often have high indicators of resilience (N=225.5, p=0.0001), engagement (N=181.11, p=0.0001), control (N=172.38, p=0.0001), risk taking (N=199.62, p=0.0001). Predictors of the formation of problematic Internet use in high school students were identified: reflexive maturity (b=-0.573, p=0.000008), regulatory maturity (b=0.387, p=0.0059), level of socialization (b=-0.407, p=0.000006) and resilience (b=0.821, p=0.000001). Using regression analysis, the role of the characteristics of personal maturity and resilience in the actual determination of the CIAS Internet addiction index was determined. Conclusion. A number of new data have been obtained that reveal the personal characteristics of adolescents with different levels of involvement in the Internet environment. The role of the features of personal maturity and resilience in the actual determination of the CIAS Internet addiction index is determined. The data obtained can be used in psychological support of modern high school students in order to diagnose and prevent problematic Internet use.