Objective : The introduction and development of the embolic protecting device (EPD) has resulted in a decreased rate of stroke after carotid artery stenting (CAS). The authors performed a retrospective study to investigate the risk factors for developing large emboli after CAS which can lead to ischemic events. Methods : A total of 35 consecutive patients who underwent CAS between January 2009 and March 2012 were included in this study. Patients were divided into two groups including those with small emboli (group A; grade 1, 2) and those with large emboli (group B; grade 3, 4). The size and number of emboli were assigned one of four grades (1=no clots, 2=1 or 2 small clots, 3=more than 3 small clots, 4=large clots) by microscopic observation of the EPD after CAS. We compared demographic characteristics, medical history, and angiographic findings of each group. Results : Thirty-five patients underwent CAS, and technical success was achieved in all cases. Twenty-three patients were included in group A and 12 patients in group B. Our results demonstrated that advanced age [odds ratio (OR) 1.24; 95% confidence interval (CI) 1.01-1.52; p=0.044] and smoking (OR 42.06; CI 2.828-625.65, p=0.006) were independent risk factors for developing large emboli after CAS. Conclusion : In patients with carotid artery stenosis treated with CAS, advanced age and smoking increased the number and size of emboli. Although use of an EPD is controversial, it may be useful in CAS in patients with risk factors for large emboli in order to reduce the risk of ischemic events.