This study investigates the association between dietary antioxidant intakes and chronic respiratory diseases (CRDs) in adults using data from the 2001-2018 National Health and Nutrition Examination Survey (NHANES). The Composite Dietary Antioxidant Index (CDAI) was calculated to assess total antioxidant capacity, including vitamins A, C, and E, zinc, selenium, and carotenoids. CRDs were defined based on self-reported physician diagnoses. Multivariate logistic regression and restricted cubic spline (RCS) regression were used to analyze the relationship between CDAI and CRDs, considering potential non-linear correlations. The study involved 40,557 participants, with a median CDAI of -0.09. Individuals in the fourth quartile of CDAI scores had a 19% lower prevalence of CRDs compared to those in the first quartile. Specifically, higher CDAI scores were associated with a lower prevalence of emphysema and chronic bronchitis. RCS regression showed a non-linear relationship between CDAI and CRDs, with inflection points at 3.20 for CRDs and 4.33 for chronic bronchitis. Stratified analyses did not identify significant effects of demographic factors on the association. The findings suggest that higher dietary antioxidant intakes are associated with a reduced prevalence of CRDs, particularly emphysema and chronic bronchitis, in the general adult population.This study investigates the association between dietary antioxidant intakes and chronic respiratory diseases (CRDs) in adults using data from the 2001-2018 National Health and Nutrition Examination Survey (NHANES). The Composite Dietary Antioxidant Index (CDAI) was calculated to assess total antioxidant capacity, including vitamins A, C, and E, zinc, selenium, and carotenoids. CRDs were defined based on self-reported physician diagnoses. Multivariate logistic regression and restricted cubic spline (RCS) regression were used to analyze the relationship between CDAI and CRDs, considering potential non-linear correlations. The study involved 40,557 participants, with a median CDAI of -0.09. Individuals in the fourth quartile of CDAI scores had a 19% lower prevalence of CRDs compared to those in the first quartile. Specifically, higher CDAI scores were associated with a lower prevalence of emphysema and chronic bronchitis. RCS regression showed a non-linear relationship between CDAI and CRDs, with inflection points at 3.20 for CRDs and 4.33 for chronic bronchitis. Stratified analyses did not identify significant effects of demographic factors on the association. The findings suggest that higher dietary antioxidant intakes are associated with a reduced prevalence of CRDs, particularly emphysema and chronic bronchitis, in the general adult population.