Cigarette smoke plays a substantial role in the development of airway inflammatory diseases, including asthma and chronic rhinosinusitis (CRS). Interleukin (IL)-17A might contribute to cigarette smoke-related inflammation of the airway. This study aimed to investigate the association between cigarette smoking and IL-17A expression in the nasal tissues of patients with CRS and asthma.We prospectively recruited 24 patients (13 smokers, 11 nonsmokers) with CRS and asthma and 6 patients with asthma but without CRS (control group) in a tertiary medical center. Nasal mucosa was obtained as part of the nasal surgery. Protein and mRNA levels of IL-17A in the nasal tissues were determined by immunostaining and real-time polymerase chain reaction.The number of unexpected emergency clinic visits for acute asthma attacks were higher among smokers than among nonsmokers. Interleukin-17A protein and mRNA levels in the nasal tissues of smokers were greater compared to those in the nasal tissues of nonsmokers (P = 0.02 both) and control patients (P = 0.05 and 0.04, respectively).Cigarette smoking was associated with an increase in the number of unexpected emergency clinic visits due to acute asthma attack and in the expression of IL-17A in the nasal tissues of patients with airway inflammatory diseases.