BACKGROUND: Few studies have been carried out to date that have addressed the epidemiology of extranodal marginal zone lymphomas (EN-MZLs). PATIENTS AND METHODS: We carried out a population-based study to investigate incidence rates (IRs) and time trends of EN-MZL diagnosed in the province of Modena (Italy) from 1997 to 2007. RESULTS: One hundred and sixty-five cases were identified from the Modena Cancer Registry that corresponded to an age-standardized IR of 2.3 cases per 100 000. A bimodal distribution of age was shown with the group of young patients mostly represented by males with cutaneous lymphoma. No time trends were observed for the IR; the incidence of gastric mucosa-associated lymphoid tissue (g-MALT) lymphomas (N = 51) markedly declined during the study period, dropping from 1.4 in 1997 to 0.2 in 2002 and then remaining stable until 2007; the calculated annual percent change for g-MALT was -17.0% (95% confidence interval -26.6% to -6.2%). We also observed a significant decrease in the rate of g-MALT associated with Helicobacter pylori (HP) infection from 61% to 17% of patients diagnosed before and after 2002 (P = 0.007; P for trend = 0.016). CONCLUSION: This population-based study provides new insights into recent changes in the epidemiology of EN-MZL, mainly represented by the sharp reduced incidence of HP-positive g-MALT lymphomas.