Lichen transplants are effective tools used to biomonitor airborne potentially toxic elements (PTEs) in urban and natural areas. The main objective of this study was to measure atmospheric PTE concentrations during the dry period in the urban and mountainous areas of Chiang Mai Province using lichen transplants. Samples of the lichen Parmotrema tinctorum (Despr. ex Nyl.) Hale were collected from a remote area and exposed at 18 sites in the Chiang Mai urban area and Doi Suthep-Pui National Park for 120 days. The concentrations of 15 PTEs, including Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Sb, Ti, V, and Zn, in the lichen transplants were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the average PTE concentrations and pollution load indices (PLIs) presented the highest values in the urban area, followed by the mountain road and forested areas. Most monitoring sites were classified as having very high pollution, and these sites were observed in all areas. This indicates that the air of some locations in the national park, including forested areas, could be contaminated by the investigated PTEs. The contamination factor (CF) values suggested that Pb, Co, Cr, Cd and Ni highly contaminate the air. These elements can originate from various sources, especially motor vehicles and biomass burning. The results of this study can be used as complementary data to traditional air quality monitoring programs to improve environmental quality in Chiang Mai Province. Keywords: Bioaccumulator · Chiang Mai · Doi Suthep-Pui National Park · Parmotrema tinctorum · Pollution load index.