ObjectiveThe purpose of our study was to evaluate the diagnostic accuracy of multidetector computed tomography angiography (MDCTA) in comparison with digital subtraction angiography (DSA) in patients with long standing diabetes mellitus and chronic lower limb ischemia. Subjects and methodsOne hundred patients with long standing DM and chronic limb ischemia underwent both CT angiography and DSA. The distal runoff of each lower limb was divided into 13 arterial segments. The status of each segment was graded as: 1, (normal or less than 10% stenosis); 2, (10–49% stenosis); 3, (50–99% stenosis); 4, occlusion. The effect of calcification on the diagnostic accuracy of CT angiography was evaluated. CTA findings were compared with DSA findings for each arterial segment. The sensitivity and specificity of CT angiography were determined using DSA as the gold standard. ResultsA total of 100 patients were included (mean age, 58years; 70% men). The sensitivity and specificity of CT angiography were significantly affected by the degree of vessel wall calcification, and increase the need for additional imaging. ConclusionVessel wall calcifications decrease the diagnostic accuracy of CT angiography in patients with long standing DM and peripheral arterial disease.