Respiratory motion causes signal blurring and reduced tumor-to-background ratio (TBR). Simultaneous PET/MR imaging uniquely allows for MR-assisted motion correction in PET imaging, potentially leading to improved PET images for detection of lesions. In this study, we implemented several MR-assisted PET motion correction methods, including gated reconstruction (gated MoCo), reconstruct-transform-average (RTA) and motion-compensated image reconstruction (MCIR), to FDG imaging of colorectal liver metastases. We quantitatively compared TBR and CNR in FDG avid liver lesions. Our results demonstrated improvement of TBR and CNR using MCIR.