We report our experience with two cases of adrenal cytomegaly, both of which were detected as cystic adrenal masses during prenatal ultrasonographic examinations. In Case 1, a left suprarenal cystic mass was detected in the fetus at 25 weeks of gestation. The mass, measuring 7 cm in diameter, did not show any change in size and was resected 26 days after birth. In Case 2, a right suprarenal lesion was found at 30 weeks of gestation. The cystic lesion, measuring 2 cm x 1.5 cm, did not change in size and was resected 3 months after birth. Adrenal cytomegaly is still not well known. It is characterized by the presence of large polyhedral cells with eosinophilic granular cytoplasm and enlarged nuclei in the adrenal cortex. This condition is thought to be a degenerative process but not a malignancy. Adrenal cytomegaly rarely forms cysts. It seemed to be impossible to diagnose preoperatively in our cases. Because of the difficulty of differentiating between cystic adrenal cytomegaly and other cystic diseases such as neuroblastoma, operative intervention is required in cases where the cysts do not decrease in size. Further study of a larger number of cases is needed to establish an optimal treatment protocol for these tumours.