The aim of our study was to compare multidetector row computed tomography (CT) angiography (MDCTA) with digital subtraction angiography (DSA) in the detection and characterization of intracranial aneurysms. Between September 2005 and May 2007, 55 consecutive patients with suspected intracranial aneurysms underwent conventional DSA and MDCTA. Thirty-two women and 23 men were enrolled in the study. The mean patient age was 54 (range = 26-79 years). All MDCTA and DSA images were independently evaluated on a workstation by two radiologists, who had 8 and 6 years of experience in CT vascular imaging and angiography. Using DSA as the gold standard, the sensitivity and specificity of CT angiography was calculated for each reader with 95% confidence intervals. The sensitivity was also calculated for aneurysms smaller than 3 mm with 95% confidence intervals. The agreement between the readers for detecting aneurysms was calculated using kappa statistics. A kappa statistic greater than 0.75 was considered an excellent agreement beyond chance, a kappa statistic of 0.4-0.75, fair to good agreement, and a kappa statistic less than 0.4, poor agreement. At DSA, 64 aneurysms were present in 50 patients involved in the study; seven patients had two aneurysms each, and four patients had three aneurysms each. In five patients, no aneurysm was detected by using MDCTA and DSA, and evaluations were considered as true negative by MDCTA. These five patients also had negative findings at repeat DSA. For readers 1 and 2, the sensitivity of MDCT in detecting aneursyms were 96.9% (95% CI = 89.3-99.1%; 62 of 64) and 98.4 % (95% CI = 91.7-99.7%; 63 of 64), respectively. The spescificity was100% (95% CI = 99.7-100%; 1,256 of 1,256) for both readers. The kappa value indicating interobserver agreement was in the category of excellent (kappa = 0.99 (95% CI = 0.97-1). Regarding the aneurysms smaller than 3 mm, for readers 1 and 2, the sensitivities were 84.6% (95% CI = 57.8-95.7%; 11 of 13) and 92.3% (95% CI = 66.7-98.6; 12 of 13), respectively. MDCTA is accurate in the detection and characterization of intracranial aneurysms and can be used as a reliable alternative imaging technique to DSA. A strategy of using CT angiography as the primary method, with DSA reserved for any cases of uncertainty, appears safe and reliable.