Purpose : The effect of concomitant use of $^{18}F$-FDG and intravenous contrast agent (CA) on dual-energy X-ray absorptiometry (DXA), was rarely reported. We had investigated these potentially confounding effects. Materials and Methods : Twenty-two patients had undergone DXA before and immediately after $^{18}F$-FDG PET/CT scans. Two DXA and 1 PET/CT scans had performed within one-day. $^{18}F$-FDG PET/CT scans had been performed with CA in 17 patients and without CA in 5 patients. Whole body bone mineral content (BMC), whole body bone mineral density (BMD), total fat mass (TFM), and lean body mass (LBM) were measured by DXA scanner before and after the $^{18}F$-FDG PET/CT scans. Results : BMC, BMD, TFM and LBM had significantly affected by $^{18}F$-FDG PET/CT with CA (BMC, +13.7%, from $2061.3{pm}393.7$ to $2343.4{pm}373.3$; BMD, +9.3%, from $1.07{pm}0.09$ to $1.17{pm}0.08$; TFM, -34.1%, from $17052.1{pm}4049.9$ to $11237.1{pm}2990.3$; LBM, +13.6%, from $45834.5{pm}5662.1$ to $52094.0{pm}6335.4$). However, $^{18}F$-FDG PET/CT without CA had no effect on the measurement of DXA (BMC, +2.4%, from $2197.7{pm}391.6$ to $2251.5{pm}380.9$; BMD, +1.8%, from $1.13{pm}0.09$ to $1.15{pm}0.07$; TFM, -6.8%, from $14585.6{pm}3455.9$ to $13591.3{pm}4351.4$; LBM, +2.2%, from $47360.5{pm}8381.8$ to $48441.1{pm}8488.1$). Conclusion : The measurements of DXA are affected by using CA. However, DXA scans might be unaffected by the presence of $^{18}F$-FDG administered for PET/CT.