PURPOSE: We aimed to use new semiquantitative parameter, maximum standardized uptake value (SUVmax)-to-Hounsfield unit density (HU) ratio for differentiation of colonic adenocarcinoma metastases from normal liver parenchyma on fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) fusion images. MATERIALS AND METHODS: We retrospectively evaluated 18F-FDG PET/CT images of 97 liver metastases from colonic adenocarcinoma in 32 adult patients. SUVmax-to-HU ratios of the metastases and non-lesion areas were calculated and compared. The correlation between SUVmax-to-HU ratio and the volume of the metastases was evaluated. Total lesion glycolysis (TLG) was obtained and correlated with SUVmax-to-HU ratios. RESULTS: The mean SUVmax, HU and SUVmax-to-HU ratio of liver metastases were significantly different than those of the normal liver parenchyma (p<0.05). There was significant correlation between SUVmax-to-HU ratios and volumes of the metastatic lesions (r=0.471, p=0.006). The correlation between TLG and SUVmax-to-HU ratio of the liver metastases was statistically significant (r=0.712, p=0.000). CONCLUSION: SUVmax-to-HU ratio is a useful parameter in differentiating liver metastases of colonic adenocarcinoma from normal liver parenchyma on 18F-FDG PET/CT images which will be helpful for staging of colonic cancer.