Background: Disparities in environmental exposures have been investigated in a multitude of epidemiologic studies. Many of these studies have demonstrated that minorities and poorer individuals were disproportionately exposed to elevated levels of air pollution and other environmental hazards. To date, differential air pollution exposures have not been assessed in a cohort of individuals with compromised respiratory health. We evaluated the distribution of air pollution exposures in such a cohort by area-level socioeconomic factors. Methods: Data from the National Emphysema Treatment Trial (NETT) (1998-2003), which included 1218 subjects ages 39-84, were linked with air pollution data from the U.S. Environmental Protection Agency Air Quality Systems database. The air pollution data included daily values of fine particulate matter (PM 2.5) and ozone. ZIP code specific exposures were spatially interpolated with the use of log-normal kriged models. This methodology was employed in order to assign exposures in areas with few nearby air pollution monitors. We investigated whether there was evidence of differential air pollution exposure by area-level measures of socioeconomic status (SES). Results: NETT participants experienced varying levels of exposure to ozone and PM2.5 and increasing cumulative pollutant exposures were associated with decreasing values of area-level SES such as median income, material deprivation, and percent unemployment. Conclusion: There was evidence of increasing air pollution exposure with decreasing area-level measures of SES. This finding adds to the literature on environmental justice and indicates that SES-related inequalities in air pollution exposure could lead to increased adverse health outcomes, particularly among individuals with existing respiratory disease.