The aim of this study was to compare the diagnostic accuracy of 18FFDG-PET/MRI with PET/CT for the detection of liver metastases. 32 patients with solid malignancies underwent 18FFDG-PET/CT and subsequent PET/MRI of the liver. Two readers assessed both datasets regarding lesion characterization (benign, indeterminate, malignant), conspicuity and diagnostic confidence. An imaging follow-up (mean interval: 185±92 days) and/-or histopathological specimen served as standards of reference. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for both modalities. Accuracy was determined by calculating the area under the receiver operating characteristic (ROC) curve. Values of conspicuity and diagnostic confidence were compared using Wilcoxon-signed-rank test. The standard of reference revealed 113 liver lesions in 26 patients (malignant: n = 45; benign: n = 68). For PET/MRI a higher accuracy (PET/CT: 82.4%; PET/MRI: 96.1%; p<0.001) as well as sensitivity (67.8% vs. 92.2%, p<0.01) and NPV (82.0% vs. 95.1%, p<0.05) were observed. PET/MRI offered higher lesion conspicuity (PET/CT: 2.0±1.1 median: 2; range 0-3; PET/MRI: 2.8±0.5 median: 3; range 0-3; p<0.001) and diagnostic confidence (PET/CT: 2.0±0.8 median: 2; range: 1-3; PET/MRI 2.6±0.6 median: 3; range: 1-3; p<0.001). Furthermore, PET/MRI enabled the detection of additional PET-negative metastases (reader 1: 10; reader 2: 12). PET/MRI offers higher diagnostic accuracy compared to PET/CT for the detection of liver metastases.