Helicobacter pylori [H. pylori], one of the most common chronic infections worldwide, is the main etiologic agent of gastritis, peptic ulcer and gastric cancer. Patients with diabetes mellitus are often affected by chronic infections. Many studies have evaluated the prevalence of H. pylori infection in diabetic patients and the possible role of this condition in their metabolic control. Some studies found a higher prevalence of the infection in diabetic patients and a reduced glycaemic control, while others did not support any correlation between metabolic control and H. pylori infection. There are only a few studies on the eradication rate of H. pylori in diabetic patients. Most of these papers concluded that standard antibiotic therapy allows a significantly lower H. pylori eradication rate than is observed in control groups matched for sex and age. Changes in the microvasculature of the stomach with a possible reduction of antibiotic absorption, the presence of gastroparesis and the frequent use of antibiotics for recurrent bacterial infections with the development of resistant strains could be some of the mechanisms underlying this phenomenon. A quadruple therapy may be used as the second line approach with a good eradication rate, even if an antibiotic selected according to a specific H. pylori antibiogram is considered the gold standard in these patients. As regards the gastrointestinal symptoms of H. pylori infected individuals, many studies showed that they are as frequent in patients with type 1 diabetes as in the general population. The incidence of H. pylori recurrence after 12 months follow-up is significantly higher in type 1 diabetic subjects when compared to controls. Reduced lymphocyte activity, neutrophil dysfunction with failure of chemiotaxis and a possible reservoir of H. pylori in dental plaque may explain the higher rate of re-infection in these patients.