Nitric oxide(NO) is a biologic mediator of various physiologic functions. Recent evidence suggests the clinical utility of fractional exhaled NO (FeNO) as a biomarker for assessing asthma and other respiratory diseases. FeNO methodologies have been recently standardized by international research groups subsequently validated in several Korean population studies. Normal ranges for FeNO have been reported for various ethnic groups and and the clinical utility has been widely evaluated in asthma and various respiratory diseases. Based on current evidence including most of Korean population data, this position paper aims to introduce the and provide guidance for the FeNO measurements Korean populations.