Liver-based metabolic disorders account for 10 to 15% of the indications for paediatric liver transplantation. In the last three decades, important progress has been made in the understanding of these diseases, and new therapies have emerged. Concomitantly, medical and surgical innovations have lead to improved results of paediatric liver transplantation, patient survival nowadays exceeding 80% 10-year after surgery with close to normal quality of life in most survivors. This review is a practical update on medical therapy, indications and results of liver transplantation, and potential future therapies, for the main liver-based metabolic disorders in which paediatric liver transplantation may be considered. Part 1 focuses on metabolic based liver disorders without liver lesions, and part 2 on metabolic liver diseases with liver lesions.