Two cases of simple renal cortical cysts in children are presented. In the first case, the cyst was detected antenatally and was followed for about 3 weeks postnatally till it was resected. The second case is an 11-year-old boy with a giant simple renal cyst exceeding 15 cm in diameter. Both cases are uncommon. The diagnostic problems regarding large intra-abdominal cystic masses are emphasized.