Aim: Platelets play a pivotal role in the pathogenesis of acute coronary syndrome (ACS), and platelet distribution width (PDW) shows the activities of platelets in circulation. The purpose of this study was to determine the association of PDW with the ACS severity and angiographic intracoronary thrombus burden and Thrombolysis In Myocardial Infarction (TIMI) flow grade. Materials and Methods: One hundred forty-nine consecutive patients who were diagnosed as having ACS were retrospectively evaluated. Global Registry of Acute Coronary Events (GRACE) scores were calculated from the clinical and laboratory data for ACS severity. TIMI flow grades and thrombus grades of the culprit coronary arteries were calculated for each patient. Patients were grouped into two groups according to their PDW values: high PDW and low PDW. The SPSS 17.0 software was used for statistical analysis. Results: PDW was found to be correlated with GRACE scores (P