Type III glycogen storage disease (GSD) is a disorder of carbohydrate metabolism caused by a deficiency of debranching enzyme. Different subtypes with different clinical pictures have been recognized. During childhood and early adulthood, the symptoms generally regress, and normal adulthood appears possible in most patients without symptoms or signs of cirrhosis. We report on an adult patient with GSD who developed endstage cirrhosis and a small hepatocellular carcinoma. She had GSD subtype IIIb, i.e., there were no signs of cardiomyopathy, myopathy, or neuropathy. She underwent a successful transplantation, representing the first case treated this way for this indication to our knowledge, and she is doing well after 1 year. Debranching enzyme activity was absent both in the liver and in the leukocytes before transplantation. The debranching enzyme activity remained absent in the leukocytes after transplantation. We conclude that patients with GSD type III may develop end-stage cirrhosis and hepatocellular carcinoma and therefore need hepatological follow-up during adulthood.