Lichen diversity and coverage on willow oaks were measured in 16 parks in the Raleigh area of North Carolina, plus one natural area in nearby Orange County (control), as a pilot study for a potential statewide lichen biomonitoring project. This study's objectives were to assess the air pollution effects of the Raleigh urban airshed on these lichen communities, and determine what methods are best for this bioassessment. Thirty-one macrolichens and 24 crustose lichens were detected with average trunk floras of 4–20 taxa per site. Lichen communities were dominated by: Buellia curtisii, Candelaria concolor, Candelariella reflexa, Lecanora strobilina, L. hybocarpa, Physcia millegrana, Pyxine subcinerea and Punctelia rudecta, of which the macrolichen species are known to be pollution-tolerant, including Py. subcinerea, which is here described as such. The control site largely lacked these species, and harbored lichens more representative of nearby protected forests. All sites lacked pollution-sensitive beard lichens (Usnea spp.) and cyanolichens that are found in protected forests. Lichen Diversity Value (LDV) analysis of macrolichens did not result in the expected pattern of increasing diversity further away from the city center, due to a number of factors. However, negative correlations were found between lichen diversity variables and human population and traffic variables, as well as between tree trunk size and crustose lichen diversity. Macrolichen species richness and abundance were higher on mossy trunks, but crustose lichen diversity was lower. Bark texture and moisture as well as air quality appeared to influence the structure and composition of these lichen communities. In summary, the lichen communities on the urban trees appeared to be affected by the region's air pollution both in terms of diversity and species composition. Diversity measures are best tracked if the total community is measured, not just the macrolichen component. Crustose lichen coverage should also be incorporated in abundance studies.