The discussion about whether the internet addiction disorder should be considered a primary addiction disorder or a secondary disorder due to other psychiatric illnesses is a very current topic. Although the term "addiction" has historically been associated with the pathological use of psychoactive substances, research over the past few decades indicates that various behaviors are also part of the spectrum of addiction. Accordingly, addictions to psychoactive substances and behavioral addictions overlap in several segments, but there are also certain differences between them. Taking into account these statements, the subject of this research was the analysis of the personality structure of Internet addicted adolescents, aimed at identifying if there are specific differences in certain personality dimensions between adolescents addicted to the Internet (reference group) and adolescents who abuse psychoactive substances, as well as in adolescents from the non-clinical population. The methodology was applied to a sample consisting of 125 respondents of both genders, aged 13 to 24, of whom 27 were from the clinical group of Internet addicts, 24 from the clinical group of psychoactive substance addicts, and 74 from the non-clinical population. A questionnaire was used for assessing Internet addiction (Internet Addiction Test) and a questionnaire for assessing the personality of adolescents (Belgrade Personality Inventory of Adolescents). The results indicate that we cannot talk about a specific profile that distinguishes respondents who are addicted to the Internet. However, despite the limitations, significant differences in certain dimensions indicate certain deviations between groups of adolescents with Internet addiction, addiction to psychoactive substances and the non-clinical population. Low research curiosity, poorly developed perseverance and goal orientation play a significant role in the aetiopathogenesis of Internet addicts. We conclude that the obtained results can have a significant role in solving the current dilemma whether Internet addiction disorder should be considered a primary addiction disorder or a secondary disorder due to other psychiatric diseases.