Background. Recent studies have shown that cerebral vascularity may be impaired in Alzheimer’s disease. Cerebral vasomotor reactivity could be an important biomarker for this pathology. Aims. The aim of this study was to investigate the alterations in cerebral vascular motor reactivity in Alzheimer’s disease subjects and to associate these changes with their cognitive scores. Methods. We recruited subjects with a diagnosis of Alzheimer’s disease and healthy controls. Demographic, clinical, imaging, and cognitive test were obtained. Then all participants performed a cerebral vascular motor reactivity test with 7% CO2 and cerebral blood flow velocities (CBFV) were recorded with transcranial doppler ultrasound before and after the test. Results. We recruited 45 subjects, 26 (21 female) Alzheimer’s disease participants and 19 (15 female) healthy controls. There were no differences in baseline cerebral blood flow velocities between the groups. After the cerebral vasomotor reactivity test, absolute mean difference in mean CBFV (ΔCBFV-m) was 8.70±4.14 versus 4.81±6.96 (p