The composition of microbiota differs between young-adult and elderly, and it is different between asthmatics and non-asthmatics. Different bacteria are related to FEV 1%. Genes related to lysine degradation, N-glycan biosynthesis, caprolactam degradation, and PPAR signaling pathway, which could be related to the reduction of inflammation and degradation of air pollutants, are higher in non-asthmatics. Genes related to the pentose phosphate pathway, lipopolysaccharide biosynthesis, flagella assembly, and bacterial chemotaxis – which may all be related to increased inflammation and colonization of pathogenic bacteria – are higher in young-adult asthmatic patients. The functional genes of airway microbiome in elderly patients are not significantly different according to asthma morbidity.