Metabolic syndrome (MetS) is occurrence of diabetes mellitus/glucose intolerance and at least two of the following: arterial hypertension, central obesity, dyslipidemia and/or microalbuminuria in the same patient (definition by WHO). Aim of the study was to find out what is the occurrence of MetS and its components in patients with acute coronary syndrome. Furthermore, we compared size of myocardial infarction expressed in “peak-CK” and “peak-MB-CK” values as a “surrogate” for myocardial infarction size in patients with and without MetS. We also analyzed myocardial infarction size according to gender in groups with and without MetS. Then we analyzed influence of particular components of MetS on myocardial infarction size and heart failure. 230 patients with acute coronary syndrome admitted at coronary care unit of University hospital Dubrava between January 2006. and June 2007. were analysed. Patients admitted in subacute phase of myocardial infarction or those that did not give consent were not included in trial. Continuous variables were expressed as mean (M) and standard deviation (SD). Dichotomous variables were expressed as percentage. Student's t test was used to compare continuous variables, and Fisher's Exact Test was used to compare dichotomous variables. A p value <0.05 was considered to indicate statistical significance. Group of patients with MetS had larger myocardial infarction size expressed by “peak-CK” (p=0.003) and “peak-MB-CK” values (p=0.002). While in patients without MetS myocardial infarction size was larger in males, on the contrary, in MetS group myocardial infarction size was larger in females. Heart failure was also more often in MetS group (p=0.012), which was again more emphasized in females, however still not statistically significant. Rate of previous myocardial infarction was again higher in MetS group (p=0.027). Hospital mortality was higher in patients with metabolic syndrome. Conclussively, we can say that group of patients with MetS, especially females having acute coronary syndrome are proned to have more extensive myocardial infarction, are more proned to have heart failure, have had more often previous infarction and have higher hospital mortality.