Background: Leukoaraiosis (LA) or white matter thinning and rarefaction are common in stroke patients. This pilot double-center study was designed to evaluate LA risk factors in stroke patients. Methods: This cross sectional study was conducted on 100 consecutive stroke patients in Walter Mackenzie Hospital, Canada and 100 consecutive stroke patients in Valie-Asr Hospital, Iran in 2004. Diagnosis of ischemic stroke and LA was performed by stroke neurologists using CT scan. The effects of race, gender, age groups, hypertension, diabetes, hypercholestrolemia and smoking on frequency rate of LA were evaluated. Results: The frequency rate of LA was the same in stroke patients living in North America or Iran. But, the frequency of LA in female stroke patients was more frequent than males (p<0.005). LA was significantly predominant in stroke patients with age≥65-yrs than those with age<65-yrs (p<0.05). The frequency of LA was significant in hypertensive patients. However, the frequency rate of LA was not influenced by diabetes, hypercholestrolemia and smoking. Conclusion: Female gender, age and hypertension seem to be the main risk factors of leukoaraiosis. In addition, there was no difference between the frequency rates of LA in patients living in Iran or North America.