PURPOSE: To evaluate the prognosis of patients with paraquat poisoning by measuring the extent of lunginvolvement, as seen on HRCT. MATERIALS AND METHODS: Forty-one patients with paraquat poisoning were treatedaccording to our hospital's routine protocol and underwent HRCT scanning 1-21(mean 7-8) days later. In 31, theresults were abnormal, and these were retrospectively analysed. Differences in the extent of lung involvement,patient age, ingested amount of paraquat, and blood WBC count were compared between the group of survivors andthose who had died. RESULTS: Among the 31 patients with abnormal HRCT findings, 11 died and 20 patients survived.The extent of lung involvement among the group of survivors was 14.8+/-14.8%; among the deceased group, it was72.3+/-16.3%. The age of the survivors was 37.5+/-13.5(11-67) years, while that of the deceased was25+/-8.9(16-41)years. Those who died showed a significantly higher extent of lung involvement than the survivors,and were younger (p<0.05). There was, however, no significant difference in blood WBC count and ingested amount ofparaquat between the two groups (P>0.05). CONCLUSION: In paraquat poisoning, the extent of lung involvement onHRCT, is useful for prediction of the prognosis and severity of poisoning.