OBJECTIVE Previous studies determined the amount of epicardial fat by measuring the right ventricular epicardial fat thickness. However, it is not proven whether this one-dimensional method correlates well with the absolute amount of epicardial fat. In this prospective study, a new cardiovascular magnetic resonance imaging (CMR) method using the three-dimensional summation of slices method was introduced to assess the total amount of epicardial fat. METHODS CMR was performed in 43 patients with congestive heart failure and in 28 healthy controls. The absolute amount of epicardial fat was assessed volumetrically in consecutive short-axis views by means of the modified Simpson's rule. Additionally, the right ventricular epicardial fat thickness was measured in two different imaging planes: long-axis view (EFT-4CV) and consecutive short-axis views (EFT-SAX). RESULTS Using the volumetric approach, patients with congestive heart failure had less epicardial fat mass than controls (51 g vs. 65 g, p=0.01). This finding was supported by EFT-SAX (2.9 mm vs. 4.3 mm, p<0.0001) but not by EFT-4CV (3.5 mm vs. 3.8 mm, p=not significant). Epicardial fat mass correlated moderately with EFT-SAX in both groups (r=0.466, p=0.012 in controls and r=0.590, p<0.0001 in patients) and with EFT-4CV in controls (r=0.387, p=0.042). There were no significant differences between EFT-4CV and EFT-SAX in controls (4.3 mm vs. 3.8 mm, p=0.240). However, in the heart failure group, EFT-4CV was significantly higher compared with EFT-SAX (3.5 mm vs. 2.9 mm, p=0.003). Interobserver variability and reproducibility were superior for the volumetric approach compared with thickness measurements. CONCLUSIONS Quantitative assessment of epicardial fat mass using the CMR-based volumetric approach is feasible and yields superior reproducibility compared with conventional methods.