Objectives: Slow coronary flow (SCF) is a phenomenon characterized by delayed opacification of coronary arteries in the absence of epicardial occlusive disease. SCF in normal coronary angiogram may or may not result in coronary perfusion defect (CPD) on myocardial perfusion single emission computed tomography (SPECT). Thus, we investigated the findings of adenosine myocardial perfusion SPECT in patients with SCF. Methods: We prospectively studied 27 patients (mean age 56 짹 11 yrs, 10 females) undergone coronary angiogram, of which finding was normal except for SCF. The SCF was determined using the frame count method. The CPD was defined as the area of defect was more than 5% of all area. After coronary angiogram, rest-stress 99mTc-Sestamibi SPECT was performed in all patients. Results: The mean coronary frame counts were 43 짹 12 in LAD, 38 짹 13 in circumflex, and 39 짹 12 in RCA. Twenty two patients were normal and 5 patients had CPD on adenosine SPECT. Of 5 patients with CPD, 4 patients had irreversible CPD, which was diagnosed as myocardial infarction, and 1 patient had reversible CPD, compatible with myocardial ischemia. The mean extent of CPD of all patients was 2.5 짹 3.3% in rest and 3.9 짹 4.5% during stress. The distributions of CPD were 41% in anterior, 37% in inferior, and 22% in lateral walls. The coronary frame counts in patients with CPD were more than those in patients without CPD (53.4 짹 12.4 vs 39.0 짹 11.9, p<0.001). Conclusion: We have shown that the SPECT findings of most patients with normal coronary angiogram but SCF were normal, however some patients had perfusion defects related to myocardial infarction and/or ischemia.