BACKGROUND AND OBJECTIVES: Drug-eluting stents (DES) have been used worldwide for conducting safe and effective percutaneous coronary intervention (PCI) for treating coronary artery disease. However, the DES might cause a higher frequency of an acute side branch occlusion or stent jails near the target lesion after PCI than that with using bare metal stents (BMS). This may be due to the eluted drug or the thick stent struts. We evaluated the clinical and angiographic outcomes of compromised side branches (stent jail) after PCI and the frequency of side branch occlusion or stent jails between sirolimus-eluting stents (SES) and paclitaxel-eluting stents (PES). SUBJECTS AND METHODS: We analyzed the clinical results and angiographic findings of 47 patients who were treated with a SES and 45 patients who were treated with a PES. We only analyzed the left anterior descending artery (LAD) and its side branches that were more than one millimeter in diameter. Side branch occlusion was defined as the development of total occlusion or a reduction of the thrombolysis in myocardial infarction (TIMI) flow more than grade 1 after stenting. The peak cardiac enzyme levels were measured. We evaluated the clinical outcomes in the hospital and at the 6 month follow up. RESULTS: There were no significant differences of the baseline clinical demographics between the SES and the PES groups. The total length and diameter of the implanted stents were 42.85+/-15.3 mm vs. 41.68+/-13.3 mm (p=0.93) and 3.09+/-0.3 mm vs. 3.1+/-0.2 mm (p=0.69) in the SES group and PES group, respectively. On average, the number of side branches of the LAD were 2.00+/-0.9 vs. 2.13+/-0.8 and on angiography after stenting, side branch occlusion and reduction of the TIMI developed in 8.51% vs. 13.33% (p=0.46) and 17% vs. 15% (p=0.88) of the SES group and PES group, respectively. The laboratory data showed that the peak creatine kinase-MB (CK-MB) and troponin-I levels were 13.5+/-31 U/L vs. 15.6+/-33 U/L (p=0.77) and 6.3+/-15 ng/mL vs. 5.42+/-9 ng/mL (p=0.77), respectively. There were no clinical in-hospital events for either group. There were no statistically significant differences in major adverse cardiac events (MACEs) at the 6-month follow up (4.3% vs. 8.9%, respectively). CONCLUSION: The clinical and angiographic outcomes of compromised side branches (stent jail) after PCI and the frequency of side branch occlusion or stent jails between SES and PES were similar.