Abstract: Objective To study the correlation between body mass index (BMI) and airway inflammation by investigating the BMI, fractional exhaled nitric oxide (FeNO), and pulmonary function in asthma patients. Methods One hundred and seventy-six asthma patients (97 females and 79 males) aged 46.35±12.86 years admitted to our department from January 2012 to December 2012 were included in this study. Their pulmonary function, exhaled FeNO and BMI were measured. The patients were divided into normal BMI group (n=83), overweight group (n=64) and obesity group (n=29) according to their BMI. Their pulmonary function and FeNO were compared. Results No significant difference was found in the FeNO and pulmonary function among different groups. BMI and FeNO were not related with pulmonary function. The FeNO level was significantly higher in male patients than in female patients. The BMI was related with the FeNO level in male patients. Conclusion BMI does not affect neither the airway inflammation nor the pulmonary function in asthma patients. Overweight or obesity may influence the condition in asthma patients via other mechanisms.