We compared the detectability of solitary pulmonary nodule (SPN) in chest radiographs displayed on different gray-scale monitor luminance. From the long-term archive of Asan Medical Center PACS 40 normal chest PA images and 40 chest PA images with SPN were fetched into the short-term storage. All Chest PA images were acquired using Fuji FCR 9501 or 9500 HQ and down-sampled from 4k to 2k pixel resolutions, and archived to ODJ with 10:1 compression ratio. Mean diameter of the nodules were 12 mm ranging in size from 8 to 20 mm. Nodules were located within the free lung fields (10 cases), overlapped with rib (13 cases), and overlapped with hilum, heart, or subphrenic areas (17 cases). Gray-scale monitors compared in our study were Image Systems M21P2KHBMAX monitor with 100 fL brightness and M21PMAX monitor with 65 fL brightness. After randomization, eight board-certified radiologists determined the presence or absence of nodules independently using worksheet. All radiologists interpreted the images displayed on low-brightness monitors, then after 10 days interpreted the images displayed on high-brightness monitors. Data were gathered using five rating categories, and ROC analysis was performed. Area under the ROC curve was compared for low and high brightness monitors. Mean area under the ROC curve for low-brightness monitor was 0.8597 and high-brightness monitor was 0.8734. Although high-brightness monitor is slightly superior to low-brightness monitor, there was no statistically significant differences between low-brightness and high- brightness monitors (p equals 0.3). Further studies are required for various other subtle lung diseases, long-term physiological effect.