Purpose: In the revascuarization of ischemic dysfunctional myocardium, stunned myocardium was reported to recover function earlier than hibernating myocardium. It was also suggested that stunning and hibernation could be discriminated by reversibility of perfusion impairment on myocardial SPECT. In this study, we investigated the time course of functional recover after CABG according to reversibility of perfusion impairment. Materials and Methods: In 92 patients with coronary artery disease, Tl-201 rest/dipyridamole stress Tc-99m-MIBI gated SPECT was performed before, 3 months after, and 17 months after CABG. Using a 20-segment model, segmental perfusion and systolic thickening were automatically quantified. Perfusion-impaired segments with abnormal thickening were classified by reversibility into reversible (REV) and irreversible (IRREV) groups. The proportions of function-recovered segments were compared between groups and also between 3 months and 17 months in each group. Results: A total of 129 segments were Included In the analysis, and 76 were REV and 53 were IRREV. At 3 months after CABG, 61 segments (80%) in REV group showed functional recovery while 28 segments (53%) in IRREV group did (p<0.001). However, at 17 months after CABG, 60 segments (79%) in REV group and 37 segments (70%) un IRREV group showed functional recovery (p=n.s.). When comparing 3 months and 17 months in each group, REV group showed no difference, while IRREV group showed significant further improvement (p<0.05). Conclusion: In viable myocardium with ischemic myocardial dysfunction, the segments with reversible perfusion impairment recover function earlier after revascularization than irreversible segments.