Background Particulate matter (PM) is a major air pollutant that has been raising global health concerns and it can cause and progress chronic obstructive pulmonary disease (COPD). To provide an effective seasonal strategy to reduce PM diameter < 2.5um (PM2.5) exposure, we performed detailed questionnaire about lifestyles to avoid PM2.5 in patients with COPD and analyzed the relationship between ambient PM2.5 and lifestyles. Methods We enrolled 104 COPD patients prospectively from four hospitals of different areas in Korea. Detailed questionnaire were conducted two times and Internet of things based sensors were installed at their home for continuous measurement of PM2.5 concentration for a year. The relationship between PM2.5 concentration, lifestyles, and COPD exacerbation were analyzed as seasons. Results Except summer, outdoor PM2.5 were higher than indoor, and the difference was the largest in winter (4.31±.02ug/m3) (Figure1). Some lifestyles were effective to reduce indoor PM2.5 compared to outdoor and effect lifestyles were different as seasons. The lifestyles which lowered annual indoor PM2.5 compared to outdoor significantly include 1) indoor air purifier operated (4.69±1.12ug/m3, p=0.001), 2) ventilating home by opening windows (-5.29±0.89ug/m3, p <0.001), 3) checking filters of the air purifier (-4.00±1.01ug/m3, p=0.031), 4) refraining from going out when outside PM2.5 is high (-3.8±1.26ug/ m3, p=0.038), 5) choosing places with little traffic when going out (-3.39±1.09ug/m3, p=0.020), and 6) windows closed while driving (-4.33±0.77ug/m3, p=0.002). The higher the economic status and educational level, the lower indoor PM2.5 was noted compared to outdoor(Figure2). There were lifestyles associated with lower small airway resistance presented as R5-R20 from impulse oscillometry and SGRQ-C and those lifestyles include checking air quality forecast and indoor mopping. Conclusion Lifestyle habits were associated with indoor PM2.5 concentrations, and they can even affect clinical outcomes including small airway resistance and quality of life in COPD.