Glycogen storage diseases (GSD) and inborn errors of galactose and fructose metabolism are the most common representatives of inborn errors of carbohydrate metabolism. In this review the focus is set on the current knowledge about clinical symptoms, diagnosis and treatment. Hepatomegaly and hypoglycaemia are the main findings in liver-affecting GSD like type I, III and IX. Diagnosis is usually made by non invasive investigations, e.g. mutation analysis. In GSD I, a carbohydrate balanced diet with frequent meals and nocturnal continuous tube feeding or addition of uncooked corn starch are the mainstays of treatment to prevent hypoglycaemia. Liver transplantation has been performed in different types of GSD. It should only be considered in high risk patients e.g. with substantial cirrhosis. Many countries have included classical galactosaemia in their newborn screening programs. A lactose-free infant formula can be life-saving in affected neonates whereas a strict fructose-restricted diet is indicated in hereditary fructose intolerance.