Many reports have been published on the long-term outcome and treatment of hepatic glycogen storage diseases (GSDs) overseas; however, none have been published from Japan. We investigated the clinical manifestations, treatment, and prognosis of 127 hepatic GSD patients who were evaluated and treated between January 1999 and December 2009. A characteristic genetic pattern was noted in the Japanese GSD patients: most GSD Ia patients had the g727t mutation, and many GSD Ib patients had the W118R mutation. Forty-one percent (14/34) of GSD Ia patients and 18%(2/11) of GSD Ib patients of ages⩾ 13 years 4 months had liver adenoma. Among subjects aged 10 years, 19%(7/36) of the GSD Ia patients and none of the GSD Ib patients had renal dysfunction. The mean height of male GSD Ia patients aged⩾ 18 years was 160.8±10.6 cm (n= 14), and that of their female counterparts was 147.8±3.80 cm (n= 9). Patients with hepatic GSDs develop a variety of symptoms but can survive in the long term by diet therapy, corn starch treatment and supportive care. Liver transplantation for hepatic GSDs is an important treatment strategy and can help improve the patients’ quality of life.