Abstract: Aim: was to assess computed tomography angiography (CTA) abilities in analysis of internal carotid artery (ICA) critical atherosclerotic lesions. Material and method: for the period 2014-2016 - 321 patients underwent examination (ultrasound and CTA of brachiocephalic arteries) prior to surgical treatment of ICA occlusive disease. CTA was made on Philips iCT 256-slice (noncontrast examination, arterial and venous phases), 50 ml on nonionic contrast agent was injected (4-4,5 ml/sec). We distinguished several types of ICA changes: stenosis more than 60% and 70%, critical stenosis, subocclusion (also with distal collapse), local occlusion. Results: CTitical ICA stenosis was detected in 82 patients (26% of all observed cases); ICA changes with diffuse decrease of upper segments - in 20 cases (6,2% of cases). Among group of decreased diameter we saw subocclusion (18 patients) and local occlusion (2 patients). In the setting of local occlusion ICA contrast-enchanced through atypical ascending pharyngeal artery In patients with diffuse decrease of upper ICA segments all elements of circle of Wills were detected in 70% of cases. During surgery CTA results were confirmed, but atherosclerotic plaque extension was higher than observed at CT approximately at 10 mm. Conclusion: we can refer critical stenosis, subocclusion and local occlusion to critical atherosclerotic ICA changes. The one should consider CTA limitations in differentiation of upper part of atherosclerotic plaque. In majority of cases decrease in ICA diameter was associated with severe atherosclerotic involvement and not with congenital changes CTA is necessary for preoperative assessment of carotid occlusive disease, especially in critical ICA changes. References 1. John J. Ricotta, Ali AbuRahma, Enrico Ascher, Mark Eskandari, Peter Faries and Brajesh K. Lal. 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