Background :Two-dimensional echocardiography (2DE) for the evaluation of LV volume and ejection fraction (EF) is based on the geometric assumptions and thus involves considerable measurement errors. Recently measurements of LV volume and EF by Live 3-dimensional echocardiography (3DE) has showed the good correlation with measurement by cardiac MRI, which is thought as non-invasive gold standard method in assessing the cardiac volume. So we compared 2DE with live 3DE in assessing the LV volume and EF in both patients with intact LV geometry and patients with distorted geometry. Subjects : We studied 48 subjects. Of 48 subjects, 26 subjects had no specific cardiac abnormality and 22 subjects had dilated LV, of whom 12 subjects were dilated cardiomyopathy (DCMP). Each patient underwent the measurements of LV end-diastolic volume (LVEDV), LV end-systolic volume (LVESV), and EF by M-mode and modified Simpson`s methods with 2DE and by endocardial border tracing in three axes with live 3DE. Results : In subjects & group with intact geometry, there was good correlation between modified Simpson`s method and live 3DE for LVEDV, LVESV, and EF. M-mode also showed good correlation with live 3D in 3 parameters. But in dilated LV group, there was no correlation between M-mode or modified Simpson`s method and live 3DE. In DCMP group, modified Simpson`s method was correlated with live 3DE for LVEDV, but no correlation was observed for other 2 parameters. M-mode was not correlated with live 3DE for all 3 parameters(Table 1). Conclusion : In assessment of LV volume and EF, 2DE is relatively useful in patients with intact geometry, but not accurate in patients with dilated LV. This emphasizes the need of more accurate, simple method in measurements of LV volume and LVEF, for example, live 3DE.