Whole body F-18 fluoro-2-deoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) has become an important method for detecting tumors, planning radiation treatment and evaluating response to therapy. However, PET/CT imaging of the lung and abdomen region is generally affected by patient respiratory motion, which can lead to underestimation of maximum standardized uptake value (SUVmax) of a region of interest, overestimation of tumor volume and mismatched PET and CT images that yield attenuation correction errors, registration errors and tumor mislocalization . The effects of partial volume and respiratory motion on SUV were investigated in previous studies . The most widely used method to correct for respiratory motion is repiratory-gated PET/CT, which divides PET data into different gates based on either temporal phase or respiratory displacement information with potential 4D CT for phase-matched attenuation correction. Guerra et al. showed that the respiratory-gated PET/CT technique is a valuable clinical tool for diagnosing lung lesions, improving quantification and confidence in reporting, reducing 3D undermined findings and increasing the overall accuracy in lung lesion detection and characterization . However, there are few hospitals in Japan in which this technique has been introduced