BACKGROUND: Reproductive health is a fundamental human right, but it is also a responsibility. Adolescence is marked by numerous changes and challenges that can often negatively impact sexual as well as general health. It was necessary to assess potential obstacles to achieving the highest level of universal health care and address them. OBJECTIVE: The aim of the study was to determine and compare the level of knowledge about reproductive health and family planning among young people in the City of Zagreb, considering the type of education, gender, relationship status, and sexual experience. Furthermore, the study assessed the ability to recognise and the tendency towards risky behaviours, as well as the adoption of healthy habits related to sexual health. METHODS: The study involved nursing and communication students from the Catholic University of Croatia, as well as 4th-grade students from the Vinogradska School of Nursing and the I. Technical School Tesla. The research was conducted in person at the premises of these institutions. A survey questionnaire designed specifically for this research was used for data collection. The questionnaire's questions were constructed with the help of a knowledge quiz available on the Sexual Health website and were adapted to the specific needs of this study. The survey consisted of 45 closed-ended questions divided into three groups. The first group of questions examined the sociodemographic characteristics of the respondents, the second group addressed knowledge about sexual health and family planning, and the third group focused on habits and attitudes related to sexual health and family planning. The overall knowledge was compared according to the type of education (health-related and non-health-related university studies or secondary schools), gender, relationship status, and sexual experience. After completing the questionnaire, students were given a leaflet with correct answers and their explanations. Descriptive statistics were used to present the data, and inferential statistics were applied to test the hypotheses. RESULTS: The study involved 334 participants. The largest groups of participants were 18 years old (56.6%), 20 years old (15.3%), and 21 years old (15.0%). At the time of the survey, the majority of participants were not in a relationship (61.3%). It was demonstrated that there was a statistically significant difference in overall knowledge about sexual health based on the type of education, gender, relationship status, and sexual experience. It was found that nursing students achieved a statistically significantly higher average rank (p=0.001) and a greater level of knowledge on questions from the survey related to sexual health compared to communication students at the Catholic University of Croatia and students from both health and non-health-oriented secondary schools. Analysis of the responses from all participants revealed that young people demonstrated the highest level of knowledge regarding the recommendation for using dual protection as a means of preventing pregnancy and sexually transmitted infections (97.9%). Additionally, 94.6% of participants were aware that a person infected with a sexually transmitted infection could appear healthy, 92.8% recognised the potentially negative impact of environmental chemicals on sexual hormones in both men and women, and 91.6% identified the statement that sexually active individuals under 25 years old are at high risk of contracting a sexually transmitted infection as accurate. The lowest proportion of correct answers was noted for questions about the abbreviation MPO (21.8%), the abbreviation HIV (33.2%), and the specialist responsible for reproductive health (30.2%). DISCUSSION: Sexual health among young people is one of the key areas of healthcare that requires special attention due to its long-term implications for physical, emotional, and social well-being. This study provided insights into the knowledge, habits, and attitudes of young people at secondary and higher education levels, with both health-oriented and non-health-oriented educational backgrounds. The results of this study were compared with findings from similar research conducted in other countries. CONCLUSION: Nursing students from the Catholic University of Croatia demonstrated a statistically significantly higher level of knowledge about sexual health compared to communication students at the same university, as well as students from health-related and non-health-related secondary schools. A statistically significant higher level of knowledge was recorded among female respondents, those in a relationship or married, and those who had sexual experience. In conclusion, the study highlighted the need to improve education on sexual health among young people in the Republic of Croatia.