The aim of this study was to analyze the fraction defectiveness and efficacy of the patient immobilization device (PID) for pediatric chest radiography. We examined 840 plain chest radiographs in six hospitals, including four children's hospitals and two general hospitals. The mean age of the patients was 1.9 years (range 0–5 years). Two board-qualified pediatric radiologists rated (into three grades, by consensus) the degree of inspiration, rotation, lordosis, scoliosis, and cutoff or coning as well as the quality of the chest radiographs. The incidence of “poor” and “very poor” quality examinations was 2/140 and 3/140 in each of two children's hospitals using PID. The corresponding figures were 9/139 and 17/140 in the two children's hospitals that did not use PID. The general hospital using PID had 14/140 “poor” and “very poor” examinations. The general hospital that did not use PID had 28/140 “poor” and “very poor” examinations. Thus, statistically better quality chest radiography was obtained with the use of PID (P < 0.001). Likewise, rotation, lordosis, and scoliosis were less frequently diagnosed as present when PID was used (P < 0.001, 0.001, 0.05). Cutoff or coning had no relation to the use of PID (P = 0.13). No significant difference was found between the degree of inspiration and the use of PID (P = 0.56). Fraction defectiveness in the general hospital that did not use PID was as much as 14 times higher than that of the children's hospitals that used PID. The patient immobilization device is recommended for hospitals with technologists not specifically trained for pediatric examination.