To evaluate the diagnostic value of pulmonary perfusion scan, we obtained 99mTc MAA per-fusion lung scan from 25 cases of airway foreign bodies. The results were as follows. 1) Significant changes in blood gases were not observed after the establishment of regional hypoperfusion caused by airway foreign body. 2) Near total or total defect was noted on perfusion scan from most of the airway foreign body. 3) There was correspondance of findings of perfusion lung scan and duration of airway foreign body. 4) After the removal of airway foreign bodies, perfusion scan abnormalities were reversed in parallel with the recovery of pulmonary blood flow. We concluded that pulmonary perfusion scan may be valuable for detection of foreign body and reversible hypoperfusion.