OBJECTIVE To observe the clinical significance of nitric oxide (NO) and 8-isoprostane (8-isoPG) changes in exhaled breath condensate ( EBC) of acute respiratory distress syndrome (ARDS) patients after treated by Qingfei Decoction (QD). METHODS Totally 48 ARDS patients receiving mechanical ventilation were equally assigned to the QD treatment group and the control group by random digit table. EBC specimens were collected by modified Ecoscreen breath condensate collector (German JAEGER Company) on the first day and the fifth day after confirmed diagnosis of ARDS. Concentrations of NO and 8-isoPG in EBC were measured by ELISA. The oxygenation index and APACHE II scores were recorded at the same time. RESULTS (1) The fatality rate in the QD treatment group was lower than that in the control group (8.3% vs 37.5%, P < 0.05). (2) After treatment NO and 8-isoPG concentrations in EBC were lower in the QD treatment group (34.49 ± 5.67 µmol/L, 30.09 ± 7.89 ng/L) than in the control group (39.78 ± 9.27 µmol/L, 35.65 ± 8.90 ng/L; P < 0.05). (3) After treatment improved oxygenation index value was higher in the QD treatment group than in the control group (120.88 ± 35.16 vs 101.50 ± 37.70, P < 0.05). After treatment APACHEII scores was lower in the QD treatment group than in the control group (6.21 ± 3.51 vs 10. 26 ± 4.33, P < 0.05). CONCLUSION Treatment of ARDS patients by QD was favorable in controlling inflammation, alleviating lung injury, and improving clinical efficacy.