Background: The lesion characteristics of in-stent restenosis (ISR) are different according to the stent type; ISR in patients treated with bare metal stents (BMS) presents with more diffuse stenosis whereas in drug-eluting stent (DES), it is more focal, even at the same stenosis severity. Such difference may affect the ���functional��� aspect of myocardial perfusion as myocardial flow is dependent on both minimum lumen diameter and lesion length. We aimed to compare the diagnostic accuracy of myocardial SPECT in patients with single vessel disease treated with either BMS or DES. Method: 114 patients with single vessel disease in whom both 6 months follow up coronary angiography and myocardial SPECT were available included in this study. The patients with ISR were grouped into BMS-ISR and DES-ISR, according to the type of stent implanted. The diagnostic accuracy of myocardial SPECT at follow up was compared between BMS-ISR and DES-ISR. Result: There was no difference in baseline characteristics between BMS (n=39) and DES (n=75) groups. 15 patients with BMS and 22 patients with DES implantation had ISR at 6 months follow up coronary angiography. The most common presentation pattern was diffuse proliferative pattern in BMS-ISR.In DES-ISR 40% presented as focal stent edge stenosis and 60% as diffuse lesions. Other angiographic characteristics such as tortuosity, eccentricity, presence of calcification, thrombosis or irregularity did not show significant difference in two groups. (p=0.762, p=0.348, p=0.352, p=0.248, p=0.822 respectively) The sensitivity and specificity of SPECT in BMS group with ISR of >50% stenosis was 83% and 69% whereas in DES they were 62% and 65% (p=0.002). When ISR of >70% was compared. the sensitivity and specificity of SPECT were 83% and 59% in BMS and 57% and 62% in DES, respectively (p=0.039). Conclusion: The diagnostic accuracy of myocardial SPECT in detecting ISR showed significant difference according to the type of stent implanted.