Abstract: AIM:To evaluate the clinical value of realtime threedimensional transthoracic echocardiography (RT3DTTE) in the diagnosis of structural heart diseases. METHODS: Two hundred and fiftysix patients ［mean age (33±9) years, 154 males］ with suspected structural heart diseases and 260 age and gendermatched normal control subjects underwent 2DTTE and RT3DTTE. Of the patients, 142 had congenital heart diseases, 85 had valvular diseases, nine had cardiac tumors and 26 had cardiac thrombi; six patients also had rheumatic mitral stenosis. The findings of 2DTTE and RT3DTTE were compared. RESULTS: Although no significant difference was found in measurements of diagnostic accuracy of structural heart diseases between RT3DTTE and 2DTTE, RT3DTTE provided a better view of the cardiac anatomic structures. RT3DTTE visualization of septal defects allowed optimal assessment of the shape, size, site and number of interatrial or interventricular defects and provided a comprehensive anatomic evaluation and characters of subtypes for complicated heart diseases such as tetralogy of Fallot and complete transposition of the great arteries. RT3DTTE could optimally visualize the surface and anatomy of mitral, aortic and other valves from multiple views, assess valvular open and close function accurately and display intracardiac masses and thrombi integrally, delineating their basal sites, shapes, sizes and relationship with adjacent structures. CONCLUSION: Application of RT3DTTE in the assessment of patients with structural heart diseases is feasible and allows more accurate anatomic and functional assessment.