Objectives: Coronary artery ectasia (CAE) is characterized by an abnormal dilatation of the coronary arteries. Red cell distribution width (RDW) is a measure of heterogeneity in the size of red blood cell. In this study, we aimed to investigate RDW levels in patients with CAE. Methods: The study population included 54 patients with CAE (28 males; mean age, 59 +/- 12) and 40 individuals comprising the control group who had normal coronary arteries (17 males; mean age, 56 +/- 10). Admission RDW was measured as part of the automated complete blood count. Results: The RDW was significantly higher in the CAE group than the control (P < .001). Also, high-sensitive C-reactive protein (hs-CRP) levels in patients with CAE were significantly higher as compared with controls (P < .001). Conclusion: This study demonstrates that RDW and hs-CRP were higher in the CAE group compared with the control group. These results show that RDW is a reliable, simple, and inexpensive marker for patients with CAE.