Background: Several studies revealed that obese patients with acute coronary syndrome may have a better outcome – the so called obesity paradox. By contrast, these data was not supported by other several studies.Methods: We evaluated 149 patients with acute ST elevation myocardial infarction (STEMI) to investigate the impact of body mass index on presentation and outcome of STEMI. Patients were classified by body mass index (BMI) into obese group (BMI ≥ 30 Kg/m2) (n=61) and non obese group (BMI ≤ 29.9) (n=88). Presence of abdominal obesity were assessed in 142 patients (waist circumference is > 102 cm in males, and > 88 cm in females) (n=72). The main points of concern to be studied are prodromal symptoms, complications, outcome, maximum and summation of ST elevation, echocardiographic parameters including wall motion score index, and severity of coronary artery disease.Results: The obese group as compared with the non obese group had lower percent of patients that had STEMI as first manifestation without prior anginal pains (p=.01). The obese group had lower mortality rate than the non obese group by an unadjusted analysis (p=.047) and. By multivariate analysis, the difference in mortality rate between both groups remained statistically significant (p=.049). Comparison between patients with abdominal obesity and patients without abdominal obesity by unadjusted analysis did not demonstrate this relationship between obesity and mortality rate. However patients with abdominal obesity had lower maximum ST elevation (p=.02), and summation of ST elevation (p=.01). Conclusion: Obese patients were less likely to have STEMI as first presentation without prior anginal pains. Obesity also was associated with a lower mortality rate during in-hospital course after ST elevation myocardial infarction and this was demonstrated also by multivariate analysis. Patients with abdominal obesity as compared by patients without abdominal obesity did not have this lower mortality rate. Maximum and summation of ST elevation as a measure of infarct size were less in patients with abdominal obesity than in patients without abdominal obesity.