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Background Eosinophilic inflammation in COPD is predictive for response to inhaled steroids. We hypothesized that inflammatory subtype in mild and moderately severe COPD can be assessed by exhaled breathmetabolomics. Methods Standardized sampling of exhaled compounds wasperformed using gas-chromatography and mass-spectrometry (GC-MS) and electronic nose (eNose) in 28 COPD patients (12/16 GOLD I/II). Differential cell counts, eosinophilic cationic protein and myeloperoxidase were measured in induced sputum. Relationships between compounds, eNose breathprints and sputum inflammatory markers were analyzedand ROC curves were constructed. Results Exhaled compounds were highly associated with sputum cell counts (9 compounds with eosinophils,20 with neutrophils:,p<0.01). Only two compounds (phenol, alkylatedbenzene) overlapped between eosinophilic and neutrophilic profiles.GC-MS and eNose breathprints were also associated with markers of inflammatory activity, in GOLD stage I (ECP: 19 compounds, p<0.01; eNose breathprint r=0.84, p=0.002) (MPO: 4 compounds p<0.01; eNose r=0.72, p=0.008). ROC analysis for eNose showed high sensitivity and specificity for inflammatory activity in mild COPD (ECP: AUC=1.00) (MPO: AUC=0.96). Conclusions Exhaled molecular profiles are closely associated with the type and activity of airways inflammation in mildand moderate COPD. This suggests that breath analysis can potentially be used for assessment and monitoring of airways inflammation inCOPD.