Objective To explore the clinical significance of IL-6 and 8-isoprostane( 8-iso-PG) in exhaled breath condensate( EBC) in chronic obstructive pulmonary disease ( COPD) and smoking. Methods 17 patients with stable COPD and 30 healthy controls( 14 smokers and 16 non-smokers) were included in this study. EBC was collected in all subjects with a self-designed experimental device. The concentrations of 8-iso-PG and IL-6 in EBC were determined by enzyme-linked immunosorbent assay. Results Both8-iso-PG and IL-6 levels significantly increased in the COPD patients [ ( 8. 37±5. 09) pg/mL and ( 4. 62 ±1. 73) pg/mL, respectively] compared with the healthy non-smokers[ ( 5. 23 ±3. 08) pg/mL and ( 3. 09 ±1. 85) pg/mL, respectively] ( both P lt;0. 01) . There was no difference between the COPD patients and thehealthy smokers( both P gt; 0. 05) . The IL-6 level significantly increased in the healthy smokers compared with the non-smokers [ ( 4. 06 ±1. 59) pg/mL vs ( 3. 09 ±1. 85) pg/mL, P lt;0. 05] , but the 8-iso-PG level was similar in the non-smokers and smokers( P gt;0. 05) . Conclusion Airway inflammation and oxide stress are persistent in stable COPD patients and are aggravated by smoking.