Patients with high body mass index (BMI) seem to have better outcomes after percutaneous coronary intervention than normal-weight patients. However, contrasting results have been reported on the “obesity paradox” in patients presenting with ST-elevation myocardial infarction (STEMI). The aim of our study was to investigate the impact of BMI on mortality in the population enrolled in the Evaluation of the Xience-V stent in Acute Myocardial INfArcTION (EXAMINATION) trial. The EXAMINATION trial randomized 1,498 patients with STEMI to a bare-metal stent or an everolimus-eluting stent. In this substudy patients were stratified into 3 groups according to BMI values: normal (BMI < 25 kg/m2), overweight (BMI = 25 to 29.9 kg/m2), and obese (BMI ≥ 30 kg/m2). The coprimary end points were the all-cause and cardiac deaths among the groups at the 5-year follow-up. BMI was available in 1,421 patients, divided in 401 (28.2%) normal, 702 (49.4%) overweight, and 318 (22.4%) obese. Obese patients were younger (p = 0.012) compared with the other groups, but with a worse cardiovascular risk profile. They were more frequently female (p <0.001) and with a higher rate of obesity-related co-morbidity conditions such as diabetes mellitus (p = 0.005), arterial hypertension (p <0.001), and hyperlipidemia (p = 0.001) compared with the other groups. At the 5-year follow-up, all-cause and cardiac deaths were less frequent in obese patients than in the other groups (p = 0.003 and p = 0.030, respectively). After adjustment for confounding variables, BMI was an independent predictor of all-cause death (hazard ratio 0.765, 95% confidence interval 0.599 to 0.979, p = 0.033), but not of cardiac death, without any interaction with the stent type. In conclusion, in patients with STEMI who underwent primary PCI, the long-term all-cause death rate decreased as BMI increased, confirming the obesity paradox, irrespective of the stent type.