Objective: To compare the clinical prognosis between patients with diffuse coronary ectasia and those with localized coronary ectasia. Design: Patients with coronary ectasia were divided into two groups based on the Markis classification (group D: types I–III and group L: type IV), and the clinical manifestations and prognosis were compared between the two groups. Results: Group D patients (52.1 ± 4 years) were significantly younger than group L patients (62.5 ± 7 years). During the study, 4 patients in group D died suddenly. Three of the patients had type I coronary ectasia, and 1 had left main coronary ectasia. Conclusion: The results of the present study indicate that patients with diffuse coronary ectasia and left main coronary ectasia should be followed carefully.