Introduction: Mitral annulus (MA) assessment is of utmost importance for the management of patients with mitral valve (MV) abnormalities and Three-dimensional transesophageal echocardiography (3D-TOE) has been the only reliable echocardiographic method for the evaluation of the mitral annulus by now. However, newer transthoracic echocardiography (TTE) probes have enabled to provide accurate measurements when TOE is contraindicated. The aim of this study is to assess the feasibility of 3D-TTE analysis of MA and the level of agreement with 3D-TOE measurements. Methods: A total of 121 consecutive patients were assessed with 3D-TTE and TOE. All MA parameters were retrospectively analyzed with the dedicated 4D-autoMVQ application. Bland-Altman analysis and intraclass correlation coefficient were used for the comparison and agreement between the two methods. Half of our patients had normal mitral valves and served as control group, while the other half had various mitral valve pathologies. Results: AutoMVQ analysis was not feasible in 11 out of 121 TTE examinations (91% feasibility) and in 4 out of 121 TOE examinations (96% feasibility). MA area and perimeter were slightly larger in TTE than those measured by TOE (12.7±3.6 vs 12.4±3.2cm2 for area and 12.7±1.7 vs 12.5±1.6cm for perimeter), however still showing strong correlation (r=0.942 and r=0.922 respectively). The majority of MV measurements were similar between the two methods with strong correlation (r>0.80). Conclusions: Assessment of the MV with 3D TTE with dedicated MVQ software is feasible and accurate, showing strong correlation and agreement with TOE measurements.