This study examined the relationship between imaginary companions phenomena, social competence and behavioral problems on croatian sample of young preschool and school-age children. Also, the goal of the research was to investigate frequency and age of occurrence of imaginary companions, some indicators of interaction between children and their imaginary companions, the characteristics of imaginary companions but also of children who create them. The study included 283 parents of children aged between 2 and 10 years, from the area of Istrian county. Parents provided informations about children's imaginary companions, social competence and internalizing and externalizing behavioral problems.Results indicate that 38.2% of the children in the sample had an imaginary companion, where the most frequent age of occurrence was around 3 years. It was more common for girls to have imaginary companions, and among the children who had an imaginary companion, most of the children were imagining only one companion who was then commonly present for a few months. For 31.5% of children their imaginary companion was the same age, and for 93% of boys and 53% of girls he was the same sex. Analysis also reveals sex differences between roles that imaginary companions played for children. The research also shows equal levels of social competence between children with or withouth imaginary companions. Parents of yong girls reported more internalizing problems than parents young boys, regardless of imaginary companion presence, and the young girls who played with their imaginary companions were more likely to have greater internalizing problems than the rest of the sample. On the other hand, boys had more externalizing problems that girls, but the effect of imaginary companions wasn't significant.The results are pointing to the existence of some differences between children with and withouth imaginary companions, as well as the possible implications of the phenomena on the positive and negative development of the child.