This review highlights the changes that have occurred in the general approach to cystic renal diseases in children. For instance, genetic mutations at the level of the primary cilia are considered as the origin of many renal cystic diseases. Furthermore, these diseases are now included in the spectrum of the hepato-renal fibrocystic diseases. Imaging plays an important role as it helps to detect and characterize many of the cystic diseases based on a detailed sonographic analysis. The diagnosis can be achieved during fetal life or after birth. Hyperechoic kidneys and/or renal cysts are the main sonographic signs leading to such diagnosis. US is able to differentiate between recessive and dominant polycystic kidney diseases, hepatocyte nuclear factor 1 Beta mutation, glomerulocystic kidneys and nephronophtisis. MR imaging can, in selected cases, provide additional information including the progressive associated hepatic changes.