Aim of the thesis: The purpose of the thesis was to inquire into the cavity prevalence in children under 12 years of age and to examine the connection between cavity prevalence in children who have attended educational institutions (nurseries and kindergartens) and those who have not, as well as between children who have older siblings and those who do not. Structure of the study: The structure of the study allows for a representation of average results obtained by conducting the study. Respondents and methods: Children under 12 years of age who visited the dental practices were included in the survey. The survey was conducted in the period from February to May 2019 in practices of the Healthcare Centre Osijek and ordination Dental Medicine Seifert d.o.o.. The survey questionnaire included questions pertaining to general data (sex and age of the child, number and age of siblings, as well as the type of the attended educational institution and the period of attendance). Results: 69 children is participated in this study. The results showed that children who attended kindergarten / nursery and who have older siblings have less caries due to education Conclusion: Based on the conducted survey, it can be concluded that cavity prevalence level is lower in children who have attended educational institutions and children with older siblings due to the fact that they are better informed. DMF index is higher in girls than boys. The acquired data prove that dental cavity remains a public health issue. DMF index data are important for setting goals and planning preventive programmes pertaining to oral health. The importance of preventive measures should be stressed through national programmes and activities, and the revitalization of preventive dental health protection should be encouraged during the early years of a child’s life, especially while attending preschool and school.