Functional mitral regurgitation (MR) results from left ventricular remodeling, leaflet tethering or tenting. Coronary artery disease is one of the important causes of functional MR due to tethering. Detection of functional MR and its severity are important factors in patient prognosis. There are different methods for detection of functional MR and its severity, including anterior mitral leaflet concavity area (AMLCA). In this cross sectional study 32 patients, 19 male with three vessel disease (3VD) who were candidate for coronary artery bypass grafting (CABG) with or without mitral valve replacement were selected. The patients had functional MR in ventriculography. AMLCA was determined by long axis view of transthorasic echocardiography (TTE). In this study 32 patients with 3VD and MR were selected (15 mild, 15 moderate and 2 cases with severe MR). The mean age was 62 ± 12 years. In these patients AMLCA were 0.1- 0.43 cm2 in transthorasic echocardiography. The findings of this study showed strong association between anterior mitral leaflet concavity area and functional MR severity (r=0.89) in parasternal long axis (LAX) view of TTE. According to these findings the relation between functional MR and AMLCA was a linear relationship and increase in severity of functional MR was in concordance with increasing of anterior mitral leaflet concavity area (P=0.001). Mitral leaflet concavity area in the parasternal LAX view provides rapid and reliable recognition of functional MR due to coronary artery disease and is quantitatively related to the degree of such MR. We recommend further study with more subjects and ischemic functional MR and AMLCA.