Introduction: Adolescents and young adults often engage in oral sex. However, the factors affecting the development of agreeing with oral sex are not clear enough.Objective: We aimed to assess the degree of agreement with oral sex among high school students and to search for background factors affecting this.Material and method: We conducted a quantitative cross-sectional study among 157 females and 38 male high school students over the age of eighteen by using an anonymous, paper-based, multiple-choice, self-administered questionnaire. For statistical analysis, we used descriptive statistics, two-sample t-tests, and Spearman rank correlation. Results: Of the respondents 67.9% were sexually active and 31.6% of them had more than one sexual partner. Of males 97.1% and of females 84.9% agreed with accepting oral sex. Degree of agreement with oral sex was higher in those who had had partnered sexual experience, and in those females who more frequently met close friends outside of school. Most participants were not in a current relationship with a partner, and for those who were, its duration did not affect the degree of accepting oral sex. The degree of agreement with the proficiency in male sexuality, and the degree of agreement with those dimensions of sexuality that most expressed the sexual drive and the desire to gratify it with the partner showed the strongest positive correlation with the degree of agreement with oral sex. In addition, the degree of agreement with the items of expressing sexual openness showed correlations with the degree of accepting oral sex. Conclusion: The degree of agreement with oral sex is high among high school students. Among the factors influencing this, the intensity of meeting friends seems to be important. We therefore recommend that the schools improve sex education in groups, highlighting the risks of oral sex, to reach the target individuals and their friends as well as their potential partners.