Sažetak The paper presents the theoretical basis of behavioral genetics methods, as well as empirical evidence regarding individual differences in personality traits. The question whether and to what extent genetic and environmental factors affect personality is one of the possible approaches to our understanding of individual differences. Behavioral genetic studies indicate that both genetics and environment contribute to the development of individual differences in personality. The review of twin, family, adoption and molecular genetic studies of individual differences in personality traits is presented. Twin studies indicate that genetic factors explain roughly 40-60% of the population variance in personality traits. On the other hand, family and adoption studies consistently show lower heritability of personality variables. Methods of molecular genetics which are used in analysis of behavioral phenotypes are also presented. As an example of these methods, studies of the relationship between novelty seeking and DRD4 gene are presented, as well as molecular genetic findings on the interaction of genes and environment.