A 14-year old girl was admitted to the Department of Paediatric Surgery of the Regional Health Centre in Opole with 4-month lasting history of increasing enlargement of the left breast. Sonography revealed a not infiltrative tumour located in the left breast; fin e needle aspiration did not evidence any malignant cells. In consequence, marginal excision of this encapsulated tumour was performed. Final histopathological examination established the diagnosis of the "juvenile fibroadenoma of breast". The postoperative period was uneventful, and the cosmetic was accepted by the patient. The rarity of malignant tumours of breast in adolescents do not exclude such possibility, however it needs careful diagnostics and conservative approach to exclude malignancy. It seems important to perform an immediate plastic repair of correction alter surgical resection of the tumour.