OBJECTIVE To evaluate the predictive role of increased corrected QT (QTc) and QT interval dispersion (QTd) on all-cause and cardiovascular mortality in a large, unselected type 2 diabetic population. RESEARCH DESIGN AND METHODS The prospective study included 1,357 type 2 diabetic patients from the Casale Monferrato Study. At baseline, QTc intervals >0.44 s and QTd intervals >0.08 s were considered abnormally prolonged. Both all-cause and cardiovascular mortality were assessed 15 years after the baseline examination. RESULTS During the follow-up period, 862 subjects per 12,450 person-years died. Multivariate analysis showed that the hazard ratio (HR) of cardiovascular mortality was significantly increased in subjects with prolonged QTd (1.26 [95% CI 1.02–1.55]) and was only slightly reduced after multiple adjustments. Conversely, prolonged QTc did not increase the HRs for all-cause or cardiovascular mortality. CONCLUSIONS Increased QTd predicts cardiovascular mortality after a long-term follow-up period in a large, unselected population of type 2 diabetic subjects.