Abstract： Objective:To explore the effect of the location and size of region of interest (ROI) on the measurement of liver fat by means of quantitative computed tomography (QCT).Methods:A total of 98 subjects who were examined with QCT for bone mineral density examination from December 25, 2019 to January 17, 2020 were recruited continuously from the Department of Health Management of Henan Provincial People′s Hospital. The liver fat content was measured by QCT workstation. The ROI was located respectively in the left lobe, the right anterior lobe and the right posterior lobe of the liver, and it was measured independently by the A measurer and B measurer. The central position of the ROI was fixed and the diameter was increased, and it was measured by the A measurer. In this study, Friedman test was used to compare the differences of measurement results in different positions or sizes of ROI, and intra-class correlation coefficients (ICC) was used to evaluate the repeatability of inter-measurers.Results:There was a significant difference for liver fat content under different positions of ROI (χ2=62.306, P<0.001), but no difference under different seizes of ROI (χ2=1.088, P=0.581). The ICC values of the inter-measurers repeatability analysis of the A measurer and B measurer in the left lobe, right anterior lobe and right posterior lobe of the liver were 0.847, 0.917 and 0.874, all more than 0.75, and the reproducibility was good. Conclusions:When QCT technique is applied to the measurement of liver fat content, the location conditions of ROI may affect results, so it is necessary to select multiple ROI in the whole liver for measurement. The inter-measurers repeatability of QCT in different parts of the liver is good.