A series of 8 cystic renal tumours is reported in seven-months to four-years-old children. The final diagnosis was cystic nephroma (multilocular cyst) in 4, cystic, partially differentiated nephroblastoma in 3 and partially cystic nephroblastoma in one. Pre-operative distinction between those three types is difficult and inadequate therapeutic approach may result from a wrong diagnosis. Progress in imaging techniques allows a better analysis of cysts and septa. If no solid part can be detected in the tumour, total nephrectomy is sufficient to obtain a favourable outcome.