The results of a secondary analysis of the empirical data collected during PISA 2018 on the sample of pupils from Serbia and Croatia are presented in this paper. Based on the theoretical model established by Pierre Bourdieu, we examined the effects of cultural capital in all three forms (objectified, embodied and institutionalized) on reading, mathematical and science competencies of pupils, measured through PISA tests. As a mediator of given variables, we put certain indicators of habitus, which is also one of the key concepts of Bourdieus' theory. The indicators which were included are adjustment to the educational system and education expectations, specifically marked as educational habitus. The results showed positive effect of all tree forms of cultural capital on a specific type of competence, while education expectations are confirmed as a mediator between cultural capital and competences. A comparative analysis of Serbia and Croatia showed that there are some differences regarding objectified cultural capital and education expectations which have stronger effect on pupil's competences on the sample from Croatia. The results of this research can be used for creating implications for educational policies which would be focused on obtaining cultural capital among pupils, therefore improving their competencies and, consequently, reducing social inequalities in education by more equal distribution of this form of capital.
