The purpose of this thesis is to review the current knowledge concerning diagnostics and treatment of abnormal uterine bleeding in the juvenile period. Abnormal uterine bleeding is one of the most common gynaecological concerns affecting women of all ages, particularly common at the extremes of reproductive age. Juvenile period, encompassing vulnerable ages of childhood and adolescence, is neglected in official diagnostic and therapeutic guidelines of international gynaecological organisations due to physiological differences compared to adulthood and a lack of studies involving girls and adolescents. Although the prevalence of abnormal uterine bleeding in adolescents surpasses that in adult women, methods of diagnostics and treatment currently in use rely heavily on experiences acquired with adults. The difference in frequency of particular causes of uterine bleeding in different age groups affects the management algorithm. Premenarcheal bleeding is rare, mostly caused by foreign bodies, trauma, and infections, while postmenarcheal bleeding, caused by non-structural entities, is relatively common. Therefore, the diagnosis of abnormal uterine bleeding in the juvenile period depends largely on detailed medical history and laboratory evaluation, while physical examination and imaging methods may help with the diagnosis of some of the less common causes. The basis of treatment of both acute and chronic bleeding is hormone therapy using estrogens and progestogens, with first-line option being combined oral contraceptives. In addition to hormonal treatment, medications used involve NSAIDs, haemostatics, and GnRH agonists, while surgical procedures mark the final therapeutic option in these age groups. The aims of treatment include cessation of bleeding, establishment of regular menstural cycle, treatment of underlying disease, and management of consequences, namely anaemia.