Aim: To investigate the association between severity of diabetic retinopathy and alterations in cerebral vasomotor reactivity in patients with diabetes by using Transcranial Doppler and breath-holding test. Methods: 43 patients with diabetic retinopathy who applied Bezmi Alem Vakıf University Neurology clinic between Jan 2013 – Jan 2014 were enrolled. Patients were classified into three categories according to grade of diabetic retinopathy and all patients underwent Transcranial Doppler examination during voluntary breath holding. Physicial examination and laboratory findings were recorded for each patient and breath-holding index was calculated. Results: The mean age of patient population was 56,51±9,34 years and the mean time from diabetes diagnosis to study enrollment was 14.49±8.06 years. 12 patients (27.9%) had mild retinopathy, 15 patients (34.9%) had moderate and 16 (37.2%) patients had severe diabetic retinopathy at the enrollment. Both calculated right and left breath-holding indexes were significiantly lower in patients with severe retinopathy compared to the patients with mild or moderate disease (right; p<0,01, left; p<0,05). Both right and left breath holding indexes were significantly lower in patients with moderate retinopathy compared to the patients with mild retinopathy (p<0,01). Conclusion: This study has shown an association between severity of diabetic retinopathy and the magnitude of serebral vascular reactivity alterations in patients with diabetes mellitus.