Background: Hepatitis C viral (HCV) infection is associated with systemic inflammation and metabolic complications that might predispose patients to atherosclerosis and increased risk of ischemic cerebrovascular disease. Aim: This doctoral thesis is aimed to assess cerebrovascular reactivity (CVR) in patients with chronic hepatitis C, and also to determine E-selectin, VCAM-1, ICAM-1 and VEGF-A serum levels in patients with chronic HCV infection in order to correlate them with CVR. Methods: Patients with chronic hepatitis C infection, as well as healthy blood donors in the control group, were assessed for CVR according to the well-established breath-holding test that uses the transcranial color Doppler (TCCD) for measurement of blood flow velocity and breath-holding index (BHI). A blood sample was taken from examinees in both groups to assess markers of endothelial dysfunction and to correlate them with CVR that was expressed as BHI determined by TCCD. Results: Results obtained during the breath-holding revealed significantly lower average peak systolic (AvPS start, P = 0.018), end-diastolic (AvED start, P = 0.031) and mean velocity values at the very beginning of the breath-holding procedure (AvmeanV start, P = 0.02), as well as a lower mean peak systolic velocity at the end of the breath-holding test (AvPS max, P = 0.02) in the hepatitis C group. CVR values, calculated as the BHI, were also significantly lower (P = 0.045) in the hepatitis C group. The obtained results revealed significant differences between the groups in all endothelial markers with the exception of E selectin. While the ICAM-1 and sVCAM-1 were significantly increased in the hepatitis group, VEGF-A was significantly decreased. No significant association between the BHI and any of the endothelial markers was found in the control group, while in the hepatitis group the scatter plot of ICAM-1 vs BHI suggested possible association. Conclusions: the results of this doctoral thesis confirm an association between a chronic HCV infection and altered CVR as well as higher levels of markers of endothelial activation (ICAM-1, VCAM-1) as possible indicators of an increased cerebrovascular disease risk.