Introduction: Every day we witness the trend of increase in the frequency of use of various substances among young people, both in Croatia and abroad. Substance abuse is already a serious health and social problem in Croatia. This research was conducted in order to turn the attention of young people to the burning issue of addiction of all types, to inform them about it accordingly, and also to provide an insight into the current situation regarding the use of addictive substances among high school students in the Šibenik-Knin County. Objectives: To collect data on the prevalence and characteristics of taking various drugs in the secondary school population in the Šibenik-Knin County and to provide an insight into the characteristics of the respondents, their views on addictive substances, the way they spend their free time and think about their future. Respondents and methods: As part of a cross-sectional study the survey of 44 questions was conducted on a sample of high school students. The properly completed surveys were collected, processed and then entered into a database. A statistical analysis was conducted using the SPSS statistical package for Windows, while percentages were used as descriptive statistical indicators of the structure and the frequency of occurrence. Results: The results show that high school students in the Šibenik-Knin County mostly do not smoke, while most occasionally consume alcohol. In terms of addictive substances, the most frequently consumed is marijuana, which is an easily-accessible drug. They prefer to spend their free time on the Internet or hang out with their friends, while games of chance are played more by boys than girls. They are satisfied and happy about their lives, but worried about their future. Conclusion: The data obtained are useful for the purpose of further planning and development of systems for prevention and protection of young people against addiction. What we should definitely pay attention to is the emergence and spread of new types of addiction.