Introduction. Cystic renal lesions are very heterogeneous lesions which differ in ethiopathogenesis, morphological and clinical manifestations, and also in evolution and therapy. Classification of cystic lesions is complex, symptomatology is poor, and diagnosis is based on complete radiological diagnostic procedures. Case report. We presented a 20-year old patient with mild subjective symptoms. Objectively, he was without positive clinical signs and changes in biochemistry of blood. Using ultrasonography (US) multiple serous simple cysts were found in both kidneys. Using computed tomography (CT) multiple serous cysts were found, without changes in cystic walls, with preserved renal parenchyma and without cystic changes on other parenchymatous organs. Conclusion. Although renal cystic lesions are frequent in adult population, this is a rare example of a young adult man with simple, gigantic, serous cysts which do not produce clinical manifestations nor functional renal difficulty so far.