BACKGROUND/AIMS Several dietary factors, such as antioxidant vitamins, have potential roles in the development of obstructive lung diseases. However, the results of studies on the relationships between dietary factors and obstructive lung diseases are inconsistent. The aim of this study was to determine which nutrients are related to airway obstruction (AO) in the Korean population. METHODS We used data obtained as part of the Korean National Health and Nutrition Examination Survey (NHANES II) in 2001. Analysis was restricted to 1,005 adults who were 18 years of age and older, who had two or more acceptable spirometry curves, and who had participated in the nutrition examination survey. AO was defined as the ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC) of less than 0.7. RESULTS Of the 1,005 study subjects, 78 (7.8%) had AO. Statistically significant factors associated with AO were 55 years of age or older (p = 0.032), central obesity (p = 0.047), hypertension (p < 0.001), smoking of 20 pack-years or more (p < 0.001), low income (p < 0.001), and low dietary protein intake expressed as a ratio of protein to recommended dietary allowance for Koreans (p = 0.037). Multiple logistic regression analyses revealed four factors that were independently associated with AO: smoking of 20 pack-years or more (odds ratio [OR], 5.801; p < 0.001), hypertension (OR, 3.905; p < 0.001), low protein intake (OR, 0.992; p = 0.004), and low income (OR, 1.962; p = 0.018). CONCLUSIONS In the Korean NHANES, smoking, hypertension, and low income were related to AO. Among dietary factors, only low protein intake was associated with AO.