Clinical symptoms and biochemical findings related to liver dysfunction are not generally reported among the presentation features of Type 1 diabetes mellitus (T1DM) in infancy and childhood. To our knowledge this is the first paper reporting two children with a clinical and biochemical picture of hepatic glycogenosis at the presentation of T1DM. In both cases at beginning of insulin therapy liver function and dimensions were absolutely normal, even though glycometabolic status had been severely altered for many days at T1DM onset. Both hepatomegaly and aminotransferase abnormalities were first found only some days after the institution of treatment with supraphysiological insulin doses. In both patients the improvement of glycometabolic control under insulin therapy was followed within some weeks by a complete physical and biochemical recovery, as typically reported in hepatic glycogenosis. These case reports demonstrate that hepatic glycogenosis can occur at any stage of T1DM and may even be one of its earliest manifestations, together with those classically reported at the onset of T1DM. Since long-standing hyperglycaemia and overinsulinisation are metabolic pre-requisites for hepatic glycogen storage, liver glycogenosis should be expected to be not uncommon during the first phases of T1DM, especially in the cases who are initially treated with supraphysiological insulin doses.