Autosomal dominant polycystic kidney disease (ADPKD) affects 1 newborn in 400 to 1000 making it the most common inherited form of genetic kidney disease and an important cause of medical morbidity and account for about 10% of end-stage renal disease. Autosomal recessive polycystic kidney disease (ARPKD) is a rare (1/20,000 to 1/40,000) inherited disease in children characterized by the association of dilation of collecting ducts and biliary dysgenesis. The clinical spectrum is variable but it represents an important cause of renal and liver-related morbidity and mortality in neonates and infancy. Symptoms of autosomal recessive PKD can begin before birth. ARPKD is genetically different from ADPKD. Parents who do not have the disease can have a child with the disease if both parents carry the abnormal gene and both pass the gene to their baby. Recently important advances in understanding the molecular basis of ADPKD (i.e. ADPKD1 and ADPKD2) and autosomal recessive PKD (i.e. PKHD1) have been done and are reported here. Genetic counselling is particularly advised in early onset disease families. It permits to determine the type of transmission, to describe the course and the major complications of the disease and to explain currents therapeutics possibilities.