Introduction: Self-efficacy is defined as a person’s belief in his or her ability to successfully perform a particular task. The effect of self-efficacy in children is an important factor in their emotional and social development. Self-efficacy as well as children's understanding of emotions are influenced by many factors such as gender, age, intelligence, personal personality or motivation of the child, the family and its environmental factors such as socioeconomic status, parental education and the quality of family relationships. Adding to their importance, emotions are functionally important for student motivation, academic success, and personality development. Methods and sample: The research was conducted through a sociodemographic questionnaire, the Self-Efficiency Questionnaire for Children by Peter Muris and the Emotion Dictionary Test by Vladimir Takšić et al. The sample consisted of 99 students: 32 elementary school students and 67 high school students. The research was conducted in April and May in the Virovitica-Podravina County. Statistical processing and analysis of data was done with the computer program SPSS Statistics, version 24.0. Descriptive (measures of central tendency and variability) and inferential statistical methods (T-test for large independent samples, ANOVA and Kolmogorov-Smirnov test of normality of distributions) were used. Results: Research has shown that male respondents have a higher level of self-efficacy compared to female respondents, but there is no difference in the results of understanding emotions with respect to gender. It was found that respondents of different age groups did not differ in the results on the self-efficacy questionnaire, however, the results showed that older respondents had a significantly higher level of understanding of emotions compared to younger respondents. Respondents attending high school have the highest score on the emotion dictionary test, while primary and vocational school respondents do not differ in the results on the emotion dictionary test, and respondents of different types of schools do not differ in the results on the self-efficacy questionnaire. The results on the self-efficacy questionnaire are not related to the results of the respondents on the emotion dictionary test. Discussion: Only 99 respondents participated in this study, and the sample itself was limited to a few grades of primary and secondary schools. The results cannot be generalized to students of other schools by extending the evaluation based on this research and it is suggested to conduct a similar research by taking a larger sample size to determine the exact difference, if any, in self-efficacy based on these variables. Given its positive impact on achievement and motivation, a better understanding of gender and age differences in the development of self-efficacy beliefs and understanding of emotions among adolescents is needed.