['This study was performed to understand how left ventricular function modulates the prognostic importance of diabetes after myocardial infarction (MI).', 'Consecutively hospitalized MI patients screened for three clinical trials were followed for a median of 7 years. Multivariable Cox regression models were used to assess the risk of mortality associated with diabetes, and the importance of diabetes was examined independently within defined left ventricular ejection fraction (LVEF) subgroups.', 'A total of 16,912 patients were included; 1,819 (11%) had diabetes. Diabetes and 15% unit depression in LVEF were of similar prognostic importance: hazard ratios (HRs) were 1.45 (95% CI 1.37-1.54) and 1.41 (1.37-1.45) for diabetes and LVEF depression, respectively. LVEF modified the outcomes associated with diabetes, with HRs being 1.29 (1.19-1.40) and 1.61 (1.49-1.74) in patients with LVEF <40% and LVEF ≥ 40%, respectively (P = 0.03).'] Does long-term prognostic importance of diabetes after a myocardial infarction depend on left ventricular systolic function?