Backgrounds Recent studies addressed the safety and efficacy of DES on diffuse long lesion. However, few data are available concerning long term outcomes of DES in terms of safety and efficacy in patients with de novo long lesion. Therefore we evaluated 3 year long term clinical outcomes of the patients with diffuse long coronary artery lesion treated with DES. Methods Between April 2003 and October 2004, 252 patients with diffuse long de novo coronary lesion (total stent length >30mm) were treated with DES (240 SES and 79 PES). Clinical and angiographic outcomes of 1 months, 6 months, 12months, 24months, and 36months were evaluated. The primary end point was the angiographic in-segment restenosis(>50% diameter stenosis at 9 months F/U). The secondary end point was the incidence of major adverse cardiac events (MACE: death, myocardial infarct, target lesion revascularization and target vessel revascularization). Results Pre-procedural reference diameter(RD), minimal lesion diameter(MLD) were 2.65짹0.58mm, 0.71짹0.44mm. Post-procedural RD, MLD were 2.91짹0.45mm, 2.61짹0.68mm. 9 months follow-up RD, MLD were 2.84짹0.42mm, 2.42짹0.79mm. 9 months angiographic ISR was 2.3%(6/252). The late loss was 0.29짹0.78mm. One case of acute thrombosis was noted among PES group(1/59). Two cases of subacute thrombosis were noted in SES group(2/193). Incidence of cumulative MACE at 6months, 12months, 24months was 5.1%(13/252), 8.7%(22/252), 9.1%(23/252), respectively. Conclusions Drug-eluting stent implantation for diffuse long de novo lesion is safe and effective in terms of low ISR and favorable long term prognosis. But the use of long term antiplatelet therapy should be further elucidated.