[en] The purpose of this study was to investigate optimum emission time of deep inspiration breath-hold (DIBH) positron emission tomography-computed tomography (PET-CT). We collected 15 PET-CT data sets by adding data of every 10 s and acquisition time ranging from 10 s (1 x 10 s acquisition) to 150 s (15 x 10 s acquisition) for both of DIBH mode and free-breathing condition (continuous mode) in phantom study. The coefficient of variation (CV) of radioactivity concentration was compared to determine optimum emission time of PET-CT. We also compared images of DIBH mode and continuous mode to clarify the influence of diaphragmatic movement in clinical setting. The mean ±standard deviation (SD) of CV in DIBH mode was 1236.3±323.1. When compared with the CV at 120 s, the relative error of CV is within 10% at 110 s (0.204), 15% at 100 s (0.212), and 20% at 90 s (0.222), respectively. Optimum emission time greater than 90 s is required to obtain clinically available images in DIBH mode. In the clinical setting, the standardized uptake value (SUV) of the lung base and measurements of uptake show little influence by respiration on DIBH PET-CT. Optimum emission time of DIBH technique greater than 90 s acquisition is preferable for clinical use. (author)