Background: In the present study, we want to demonstrate the correlation between obstructive sleep apnea syndrome (OSAS) whose independent effect on carotid artery intima-media thickness (IMT) was demonstrated, with Framingham risk score (FRS) showing the overall cardiovascular risk. Methods: IMT of the carotid artery was measured with ultrasonography and 10-year risk of coronary heart disease (CHD) was defined with FRS in 90 consecutive patients referred to our sleep clinic and who underwent polysomnography (PSG), with vascular risk factors and without a clinical atherosclerotic disease. Results: IMT and FRS were found to be statistically significantly increased in the severe OSAS group compared to the other two groups. Carotid IMT was found to be significantly positively correlated with, apnea-hypopnea index (AHI), oxygen desaturation index (ODI) and time duration with oxygen saturation (SpO2) <90%, and negatively correlated with minimum oxygen saturation at sleep (minimum SpO2) and mean SpO2. In control and mild OSAS group IMT and FRS have significantly positive correlation (r: 0.501, P: 0.027; r: 0.625, P<0.001), while in severe OSAS group no significant correlation was detected between IMT and FRS (r: 0.321, P: 0.06). In the regression analysis AHI and ODI were found to be an independent predictor of carotid IMT. ODI was found to have an independent effect on the progression of atherosclerosis. Conclusions: Increased carotid IMT in severe OSAS group could not be explained with the classical risk factors. In this respect, FRS might be insufficient to determine correctly the cardiovascular risk and protection strategies against the disease in OSAS patients.