The topic of this thesis is focused on the positive development of high school students in Split. The theoretical part of the thesis explains the concept of adolescence, which is described as the developmental period between childhood and adulthood. Furthermore, the thesis elaborates on the concept of positive youth development, with a special emphasis on the 5C model of positive development, which includes five key characteristics: (1) competence, (2) confidence, (3) connection, (4) character and (5) caring. To write this thesis, research was conducted on a sample of N = 248 high school students from Split, with the aim of examining the 5C characteristics of positive youth development. Specifically, the prevalence of 5C characteristics among high school students in Split was examined, as well as differences in 5C characteristics between male and female students, and the relationship between sociodemographic characteristics and 5C characteristics. The research was conducted as part of the e larger scientific project Testing the 5C framework of positive youth development: traditional and digital mobile assessment (P.R.O.T.E.C.T.).