We report two new cases of liver glycogen synthase deficiency (GSD0). The first patient presented at the age of 8 months with recurrent hypoglycemic seizures. The second patient presented at 14 months with asymptomatic incidental hyperglycemia. Glucose monitoring in both patients revealed daily fluctuations from fasting hypoglycemia to postprandial hyperglycemia. Genetic analysis of the GYS2 gene confirmed the diagnosis. GSD0 is more common than previously assumed. Recognition of the variable phenotype spectrum of GSD0 and routine analysis of GYS2 are essential for the correct diagnosis.