International Journal of Environmental Research and Public Health vol. 17 br. 16 str. 5816-5816 Abstract: The aim of this paper was to investigate the level of influence of online media on the parents’ attitudes toward vaccination of children in three countries of the Western Balkans—Montenegro, Serbia, and Bosnia and Herzegovina, in order to use the potentials of this form of communication effectively and efficiently. Online media are a critical factor of influence on the formation of attitudes in many areas of modern society, which is why their proper use plays an important role in strengthening vaccine confidence and which may further contribute to improvement of public health. On the other side, having in mind the fact that communication is an integral part of marketing, it is clear that social marketing has an extremely important role regarding the analyzed topic, especially because of the fact that social marketing activities tend to change or maintain people’s behavior for the benefit of individuals and society as a whole. For the purpose of this research, a conceptual model was developed. Quantitative research was conducted online in the first quarter of 2020 using the survey method. Statistical analysis was applied to data collected from 1593 parents in the analyzed countries. The relevance of the hypotheses was tested using standard statistical tests, ANOVA test, eta coefficient, and logistic regression. The research showed that all analyzed variables from the model have a significant impact on the parents’ attitudes toward the vaccination of children and that they correlate with the degree of trust in vaccines. The results also approved that online media have a significant influence on the formation of parents’ attitudes toward the vaccination of children (obtained values of eta coefficient η 2 = 0.216, η 2 = 0.18, η 2 = 0.167, η 2 = 0.090, reliability Cronbach’s Alpha 0.892), which confirms the importance of the use of social marketing in order to direct communication properly and to strengthen the level of trust in vaccines. Additionally, the results of logistic regression showed that the following groups of parents are particularly vulnerable to the influence of online media on attitudes toward vaccines: women, parents of younger age (“millennials”), and parents who are in common law marriage, as well as parents who have more children. In addition, the results showed that there is no statistically significant difference in the attitudes of parents in the observed countries (η 2 = 0.000, F = 0.85). Based on the results of the research, the authors suggest that decision makers should pay more attention to modern forms of online communication and social marketing in order to use their potential for improvement of public health, as well as avoid the harmful impact that certain forms of communication may have on the formation of attitudes and loss of confidence in vaccines. The findings provide an important contribution for public health policy makers to identify and understand properly the impact of online media and social marketing and thus to better adapt their initiatives to changes in modern society. The Impact of Online Media on Parents’ Attitudes toward Vaccination of Children—Social Marketing and Public Health Melovic, Boban Jaksic Stojanovic, Andjela Backovic Vulic, Tamara Dudic, Branislav Benova, Eleonora info:eu-repo/semantics/article eng https://unilib.phaidrabg.rs/o:5449 doi:10.3390/ijerph17165816 2020-08-11 http://creativecommons.org/licenses/by/4.0/legalcode application/pdf 737047 bytes Keywords: online media; social media; vaccination; social marketing; public health