AIMS: Radionuclide techniques, and recently MRI, have been used for clinical evaluation of right ventricular (RV) volumes function (RVEF) and volumes; but with the introduction of 3D echocardiography, new echocardiographic possibilities for RV evaluation independent of geometrical assumptions have emerged. This study compared classic and new echocardiographic and radionuclide estimates, including gated blood pool single-photon emission computed tomography (SPECT) of RV size and function to RV volumes, and ejection fraction (RVEF) measured by magnetic resonance imaging (MRI). METHODS AND RESULTS: Thirty-four subjects with (a) prior inferior ST-elevation myocardial infarction (n=17), (b) a history of pulmonary embolism and persistent dyspnea (n=7) or (c) normal subjects (n=10) had 2D and 3D echocardiography, SPECT and MRI within 24h. End-diastolic volume and peak tricuspid regurgitation velocity were increased in patients with a history of pulmonary embolism compared to healthy subjects, 130+/-26 ml vs. 94+/-26 ml, P<0.05, and 3.3+/-1.1m/s vs. 2.3+/-0.3m/s, P<0.05, respectively, whereas no differences in RVEF were seen in the three groups. Echocardiographic as well as SPECT estimates of RV volume showed significant correlation to RV volumes by MRI. Tricuspid annular plane systolic excursion (TAPSE) had the better correlation to RVEF by MRI, r=0.48, P<0.01; whereas 3D echocardiography had a correlation of 0.42, P<0.05. Compared to MRI, 3D echocardiography underestimated RVEF by 5.9%, 95% limits of agreement 1.6-10.2%. CONCLUSION: 3D echocardiographic estimates of RV size and RVEF show only moderate correlation to MRI measures of these parameters, and simple 2D echocardiographic estimates of RV size and function show similar correlations. For routine clinical purposes the simple TAPSE may be preferred over 3D and SPECT techniques for RVEF estimation.