Stent thrombosis is a devastating complication after percutaneous coronary intervention (PCI), but the influence of obesity on risk of stent thrombosis is unclear, and it is unknown if this relation is dependent on stent type. The objective of this study was to examine the relation between body mass index (BMI) and stent thrombosis after PCI with bare-metal stent (BMS) or drug-eluting stent (DES). We followed 5,515 patients who underwent PCI with implantation of ≥1 BMS or DES at a high-volume tertiary invasive cardiology center from 2000 through 2006. Only patients with a single type of stent (BMS or DES) implanted at the index PCI were included. Median follow-up period was 26 months (interquartile range 12 to 44) and definite stent thrombosis occurred in 78 patients. Hazard ratio of definite stent thrombosis adjusted for number of stents at the index PCI was 0.92 (95% confidence interval [CI] 0.86 to 0.97) for each increase in kilograms per square meter of BMI. There was no significant interaction between stent type and BMI (p = 0.48). Hazard ratios for probable stent thrombosis and possible stent thrombosis adjusted for numbers of stents at the index PCI were 1.01 (CI 0.99 to 1.03) and 0.99 (CI 0.98 to 1.01) for each increase in kilograms per square meter of BMI, respectively. In conclusion, BMI was inversely correlated with risk of definite stent thrombosis after PCI irrespective of stent type.