Renal malformations represent the most common manifestation of congenital diseases in childhood. Renal agenesis, dysplasia, hypoplasia, and cystic renal diseases are such entities. Causes vary; partially they derive from the complex renal organogenesis, and partially they have a genetic background. Today there is evidence that disturbances of the cilium-centrosome complex form the pathogenetic base of most or many phenotypically different cystic renal diseases on a cellular level; thus, they are summarized under the term “ciliopathies” (Guay-Woodford 2006; Hildebrandt 2005; Hildebrandt et al. 2011). Furthermore, uromodulin – a urinary mucoprotein former known as “Tamm-Horsfall protein” – appears to play an important role in the genesis of cystic kidney diseases (Iorember and Vehaskari 2014). The knowledge of the individual etiology and development helps to understand the disease process, affects further diagnostic and therapeutic management, and helps to properly estimate prognosis of these patients and their families, respectively. The clinical and genetic basics including the relevant queries toward imaging are discussed in chapters “Genetics in Nephrourology” and “Renal Agenesis, Dysplasia, Hypoplasia, and Cystic Diseases of the Kidney”.