Background: Several reports have shown that in patient with ST-segment elevation acute myocardial infarction (STEMI) longer ischemia time is associated with impaired reperfusion and higher mortality. However, there is still some doubts with regards time to reperfusion role in patients treated with primary percutaneous coronary intervention (PCI). Therefore, the aim of the current study was to evaluate the impact of time-totreatment on infarct size as evaluated by myocardial scintigraphy in a large cohort of STEMI patients undergoing primary PCI. Methods: Our population is represented by 830 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99m-sestamibi. Conclusions: This study shows in a large population of STEMI patients undergoing primary PCI that time-totreatment is linearly associated with infarct size.