Purpose: To systematically compare MRI-and CT-based measurements of both the volume and quality of epicardial adipose tissue (EAT). Materials and Methods: This prospective study included participants from a subset of the Swedish CArdioPulmonary bioImage Study (SCAPIS) who underwent MRI and CT between November 2017 and July 2018. Dixon fat-water separation MR images were manually segmented, and a threshold-based approach based on a fat signal fraction (FSF) map was used to obtain the EAT volume. Within this EAT volume, the mean FSF was quantified as a measure of fat quality. EAT segmentation from CT images was performed using deep learning techniques, and the EAT volume and its mean attenuation were quantified. Correlation between MRI-and CT-based measurements of EAT volume and quality was assessed using the Pearson correlation coefficient. Results: Ninety-two participants (mean age, 59 years +/- 5 [SD]; 60 male participants) were included. The intermodality correlation for EAT volume was very strong (r = 0.92, P < .001), with systematically larger values for CT versus MRI (P < .001). There was a strong negative correlation between MRI FSF and CT attenuation (r = -0.72, P < .001). Repeatability analysis for assessment of MRI EAT volume showed good interreader agreement (intraclass correlation coefficient, 0.86) and excellent intrareader agreement (intraclass correlation coefficient, 0.96). Conclusion: Correlation between MRI and CT was very strong for EAT volume and strong for EAT quality.