RESULTS: We found lower FeNO levels and EOS% in COPD patients than in asthma patients (17.41±13.84ppb versus 57.58±46.61ppb and 1.23±1.73 versus 8.42±7.38; P<0.01, respectively). FeNO levels in COPD patients were within Chinese healthy adult normal range (mean:16ppb,95%CI:5∼30ppb, P>0.05). Serum CRP levels in COPD patients were higher than in asthma patients (9.94 (60.10) versus 2.49 (11.79), P<0.05). Pulmonary function parameters (including FEV1, FEV1% pred, FVC, FVC% pred, FEV1/FVC and FEF25%, FEF50%, FEF75%) in asthma patients were better than in COPD patients (P<0.05, respectively). There was no correlation between FeNO and lung functions parameters, EOS% in COPD patients (P>0.05, respectively). In asthma patients we also found no correlation between FeNO and lung functions parameters (P>0.05, respectively), however, there was positive correlation between FeNO and EOS% (r=0.626, P<0.01).