Purpose Standardized uptake values (SUVs) normalized by lean body mass (LBM) determined by CT were compared with those normalized by LBM estimated using predictive equations (PEs) in normal liver, spleen, and aorta using $^{18}F$-FDG PET/CT. Methods Fluorine-18 fluorodeoxyglucose (F-FDG) positron emission tomography/computed tomography (PET/CT) was conducted on 453 patients. LBM determined by CT was defined in 3 ways ($LBM_{CT1-3}$). Five PEs were used for comparison ($LBM_{PE1-5}$). Tissue SUV normalized by LBM (SUL) was calculated using LBM from each method ($SUL_{CT1-3}$, $SUL_{PE1-5}$). Agreement between methods was assessed by Bland-Altman analysis. Percentage difference and percentage error were also calculated. Results For all liver $SUL_{CTs}$ vs. liver $SUL_{PEs}$ except liver $SUL_{PE3}$, the range of biases, SDs of percentage difference and percentage errors were -0.17-0.24 SUL, 6.15-10.17 %, and 25.07-38.91 %, respectively. For liver $SUL_{CTs}$ vs. liver $SUL_{PE3}$, the corresponding figures were 0.47-0.69 SUL, 10.90-11.25 %, and 50.85-51.55 %, respectively, showing the largest percentage errors and positive biases. Irrespective of magnitudes of the biases, large percentage errors of 25.07-51.55 % were observed between liver $SUL_{CT1-3}$ and liver $SUL_{PE1-5}$. The results of spleen and aorta $SUL_{CTs}$ and $SUL_{PEs}$ comparison were almost identical to those for liver. Conclusion The present study demonstrated substantial errors in individual $SUL_{PEs}$ compared with $SUL_{CTs}$ as a reference value. Normalization of SUV by LBM determined by CT rather than PEs may be a useful approach to reduce errors in individual $SUL_{PEs}$.