Current STEMI guidelines focus on early diagnosis and treatment of myocardial infarction in the pre-hospital phase so as to eliminate unnecessary delays in receiving PPCI. However, still the most important issue is to open the occluded infarct related artery andrestore normal blood flow and myocardial perfusion. These may be achieved by reperfusion strategies: pharmacological and/or mechanical. The aim of this study was to assess the angiographic paramaters, myocardial perfusion and cardiac magnetic resonance (CMR) parameter evaluation in STEMI patients after initial lytic therapy transferred for immediate PCI. Patients with acute MI according to the definition and with time from chest pain onset to PCI >90 minutes were included in this study. All patients received heparin bolus 40 U/kg, 15 mg alteplase and 0.25mg/kg abciximab and were immediately transferred to cathlab. Alteplase (35mg/60min) and abciximab (0,125 ug/kg/min) infusions were continued during transport. Patients after successful lysis (full ST segment resolution in ECG, TIMI 3 in angiography and lack of chest pain) were randomly assigned to either immediate PCI or delayed PCI (3-5 days). CMR was performed at 12 month follow up. There were 96 patients enrolled: 48 to group A (immediate PCI) and 48 to group B (delayed PCI – median time delay was 3 days). CMR was performed in 20 patients in Group A and 24 patients in Group B. There was a trend towards worse myocardial perfusion in immediate PCI group (tMPG 2+3 88% vs 67%, p=0.06). Patients in delayed PCI group had better (although statistically insignificant) spontaneous perfusion grade after 3 days (tMPG2+3 81% vs 91%, p=0.2). There were no differences in infarct size measured in CMR in both groups (10,1±10 vs. 10,5±5, p=NS). However, patients with immediate PCI presented higher LV end-systolic and diastolic volumes. The LV ejection fraction was significantly lower in patients after immediate PCI. In two patient in delayed group recurrence ischemia with urgent PCI occurs during hospitalization. There were no haemorrhagic strokes. Also no differences in major bleeding complications were not observed. Immediate percutaneous coronary intervention for ST-elevation myocardial infarction after initial lytic therapy with TIMI 3 flow is efficacious but does not improve myocardial perfusion. PCI delay is associated with additional recurrent ischemia (urgent PCI). However delayed angioplasty influences better myocardial perfusion. Infarct size is comparable in the groups. However immediate angioplasty after successful fibrynolisis may course left ventricular functionworsening in long term follow up.