Aim: High definition(HD) Computed Tomography(CT) was presented as an improvement in CT technology which is known to have increased in sharpness of the edges of the vessels and stents in vitro. The purpose of the study was to take the effectivity of this technology clinically by evaluating the diameter and wall thickness of carotid vessels in stroke patients. Material and Method: CT Angiography(CTA) of carotid arteries; 19 with HDCT and 21 with standard definition(SD) CT, totally 40 stroke patients were examined in different University hospitals with the same imaging protocols. The vessel wall inner and outer diameters and thickness of common, internal and external carotid arteries (CCA, ICA and ECA) were assessed by two blinded radiologists. Comparison was made between the scanners for image quality, motion artefacts and image noise. Results: HD and SD CT angiography achieved comparable. The agreement of the radiologists and Cronbach Alpha value was higher in HDCT showing that vessel contours are sharper in HDCT images and measurements are more reliable. Discussion: Due to new gemstone technology image quality was improved in HDCT angiography, is found much more effective than SDCT to show the edges of the vessel wall so qualifies the establishment of the plaques and extent of osteal stenosis.