OBJECTIVES: The benefits of inhaled corticosteroids (ICS)in patients with asthma or chronic obstructive pulmonary disease (COPD) are based mainly on their anti-inflammatory effects. Chronic inflammation has been implicated in the pathogenesis of several cancers, including lung cancer and laryngeal cancer. The aim of this study was to elucidate the association between ICS use and diagnosis of lung cancer and laryngeal cancer. METHODS: A nested case–control study was conducted based on the Korean national claims database. The eligible cohort consisted of 792,687 new adult users of inhaled respiratory medications between January1, 2007, and December31, 2010. Patients diagnosed with lung cancer or laryngeal cancer after initiation of inhaled medication were identified as cases. For each case individual, up to five control individuals matched for age, sex, diagnosis of asthma or COPD, Charlson Comorbidity Index scores, number of health care visits, and initiation date were selected. RESULTS: From the cohort population, 9,177 individuals diagnosed with lung cancer were matched with 37,048 controls. Additionally, 408 individuals with laryngeal cancer and 1,651 controls were matched. ICS use was associated with a decreased rate of lung cancer diagnosis [adjusted odds ratio (aOR), 0.79; 95% confidence interval (CI), 0.69–0.90]. Furthermore, the association between ICS use and decreased risk of lung cancer was dose dependent (P<0.0001 for the trend). However, no reduction in the risk of laryngeal cancer among ICS users was identified (aOR, 1.06; 95% CI, 0.62–1.18). CONCLUSIONS: The use of ICS is associated with a reduced risk of lung cancer but not of laryngeal cancer.