Background : In recent studies, by utilizing single photon emission computed tomography(SPECT) and magnetic resonance angiography(MRA), anatomical and functional evaluation became possible. Although MRA is replacing conventional angiography, gold standard for investigating anatomical structures is still that. We studied the correlation between internal carotid artery(ICA) stenosis, patterns of collateral pathway, and cerebrovascular reserve using transfemoral cerebral angiography(TFCA) and SPECT. Method : We studied 54 patients with symptomatic ICA stenosis who were visit to our hospital between Sep 2009 and May 2011. Forms of collateral pathway were classified into primary and secondary pathway group. Severity of ICA stenosis was divided into 4 stages. Vascular reserve on SPECT was classified into favorable and poor group. Result : As a result of TFCA, collateral pathways were observed in 44 of 54 patients. Via anterior communicating artery(AcoA) pattern occupied the highest proportion and other major patterns were via posterior cerebral artery-middle cerebral artery(PCA-MCA) and via posterior communicating artery(PCoA) pattern. Twenty-eight patients were primary pathway group and 16 patients were secondary pathway group. In both groups, most of patients had moderate or severe ICA stenosis. As a result of SPECT, favorable vascular reserves were observed in 17 of 54 patients. Most of them had mild ICA stenosis and/or primary collateral pathway. Contrarily, most of secondary pathway group had poor vascular reserve even if their ICA stenosis severity was mild. Conclusion : In patients with symptomatic ICA stenosis with collateral pathways, rate of primary collateral pathways was higher than secondary collateral pathways. Secondary collateral pathways had insufficient compensatory effect about reduced cerebral blood perfusion.