Ovarian masses may result from functional (nonneoplastic) cysts or benign or malignant neoplasms. In 1973, the World Health Organisation classified ovarian neoplasms into nine major categories and 26 subtypes, based on histologic cell type and benign versus malignant state. The literature review concerning functional ovarian cysts in girls has been presented. Functional cysts are not true neoplasms but rather should be considered a variation of a normal physiologic process. Functional cyst include follicular, corpus luteum, and theca-lutein types, all of which are benign and usually self-limited. The incidence of functional cysts in the community is probably even higher than indicated in most series, as percentages are based on referred cases and it is not possible to determine the underlying incidence of nonidentified or asymptomatic cysts. Incidence, etiopathogenesis, clinical symptoms, methods of diagnostics, treatment and results of functional cysts in fetus and newborns, in children and adolescents are discussed.