Chronic obstructive pulmonary disease (COPD) is a progressive disorder of the lung parenchyma and airways, which is the third-leading cause of death in the USA. Current therapies for COPD are only partially effective and may also have side effects. Although increasing evidence indicates that quercetin supplementation may be beneficial in treating COPD, key methodological issues have not been resolved. The overall objective of this study is to determine the dosage of quercetin supplementation, bioavailability of quercetin, safety, dose-response relationship and appropriate biomarkers which reflect clinical outcomes in patients with COPD that is necessary for conducting large clinical trials in this patient population.