The aim of the present study was to investigate whether reperfusion by primary percutaneous coronary intervention (PCI) improves 12-month survival in late presenters with ST-segment elevation myocardial infarction (STEMI). We analyzed 2,036 patients with STEMI presenting 12 to 24 hours from onset of symptoms, without cardiogenic shock or pulmonary edema and not reperfused by thrombolysis, of 23,517 patients with STEMI enrolled in the Polish Registry of Acute Coronary Syndromes from June 2005 to August 2006. An invasive approach was chosen in 910 (44.7%) of late presenters and 92% of them underwent reperfusion by PCI. Patients with an invasive approach had lower mortality after 12 months than patients with a conservative approach (9.3% vs 17.9%, p <0.0001). The benefit of an invasive approach was also observed after multivariate adjustment with a relative risk 0.73 for 12-month mortality (95% confidence interval 0.56 to 0.96) and in a subpopulation of patients selected by a propensity-score matching procedure with an adjusted relative risk 0.73 for 12-month mortality (0.58 to 0.99). In conclusion, almost 1/2 of late presenters with STEMI were considered eligible for reperfusion by primary PCI. These patients had a lower 12-month mortality rate than they would have had if they had been treated conservatively, which supports the idea of late reperfusion in STEMI. However, whether all late presenters with STEMI should be treated invasively remains unanswered. Nevertheless, until a randomized trial is undertaken, late presenters with STEMI could be considered for reperfusion by primary PCI.