Background: The aim of this study was to assess the effects of percutaneous transluminal angioplasty with stenting on cerebral vasoreactivity in carotid stenosis (CS). Methods: We studied the changes in the middle cerebral artery using transcranial Doppler and the breath-holding index (BHI) after hypercapnia in 33 patients with CS (15 symptomatic, 18 asymptomatic) before and 1 day and 1 month after stenting. Results: One day after stenting, the BHI significantly increased (p < 0.01) on the previously stenotic side in all patients. One month after stenting, the BHI was significantly higher on the contralateral side of asymptomatic (p < 0.05) and symptomatic patients (p < 0.01). Conclusion: Percutaneous transluminal angioplasty with stenting results in increasing improvement close to normalization of impaired cerebral vasoreactivity in patients with symptomatic and asymptomatic high-grade CS.