Unilateral renal cystic disease (URCD) is a rare multicystic kidney disease, characterized by replacement of renal parenchyma by a cluster of multiple cysts with a normal contralateral kidney. The gross and pathological findings of URCD are not different from those of autosomal dominant polycystic kidney disease (ADPKD). The diagnosis of URCD is required to have the characteristic CT findings in addition to genetic and clinical manifestations. The most important different diagnosis is ADPKD, from which it differs by being unilateral, having a negative family history and a lack of progression to chronic kidney disease. In this report, we describe a unique case of unilateral renal cystic disease in a 69-year-old female who visited our clinic for evaluation. It may be important to distinguish URCD from ADPKD because even they have similar clinical characteristics but genetic background and clinical outcomes are different.