OBJECTIVE Reporting on three cases of gastric neuroendocrine tumors (g-NETs) in patients taking long-term proton pump inhibitors (PPIs). These tumors are not classifiable considering current criteria. g-NETs are currently grouped as: types 1 and 2, related to hypergastrinemia due to chronic atrophic gastritis and Zollinger-Ellison syndrome respectively, and type 3, normogastrinemic and more aggressive. Although the g-NETs onset in patients taking PPIs is biologically plausible, only a few cases have been reported so far. MATERIALS AND METHODS From January 2005 to July 2014, 31 g-NETs were referred to our Unit: 24 (77%), one (3%) and three (10%) resulted types 1, 2 and 3, respectively. Three cases (10%) did not meet the current classification criteria. RESULTS The three patients were administered long-term PPIs for gastro-esophageal reflux disease. Patient 1: a 78-year-old man, with a 4-mm well-differentiated g-NET (Ki-67<1%) and marked hypergastrinemia. Patient 2: a 58-year-old man affected by a 6-mm well-differentiated (Ki-67 = 4%) g-NET, with normal gastrin levels. Patients 3: a 67-year-old woman with an 18-mm well-differentiated g-NET (Ki-67 <2%), with mild hypergastrinemia. In the three patients, histology and pertinent blood tests excluded chronic atrophic gastritis, Helicobacter pylori infection or Zollinger-Ellison syndrome. The first two patients underwent endoscopic polypectomy; in the third case total gastrectomy was performed. Further clinical, endoscopic and imaging follow-up did not show any g-NET recurrence. CONCLUSIONS The present data point to the existence and epidemiological relevance of g-NETs associated with PPIs intake. These neoplasms are not included in the current classification, thus their treatment and follow-up have not been established.