The antiplatelet effect of clopidogrel prodrug is characterized by a wide inter-individual variability that has a significant clinical relevance. Among varios factors that are involved in the occurrence of clopidogrel resistance, the genetic polymorphisms play a key role. The aim of the present study was to investigate the impact of some risk factors for atherosclerosis on the antiplatelet effect of clopidogrel in patients with acute coronary syndrome and the possible correlation with metabolizer phenotype of patients based on CYP2C19 polymorfisms. We found a statistically significant correlation (p value [ 0.05) between smoking or dyslipidaemia and the presence of ultrarapid metabolizer phenotype for clopidogrel in our research population.