Multidimensional Gas Chromatography-Time of Flight Mass Spectrometry is a relatively new, highly versatile and productive technique that is ideally suited for the detection of PACs in environmental samples. Air samples collected in Slocan Park in Vancouver and in Langley, BC (a semi-rural site) during the PACIFIC 2001 field study and aerosol samples from St. Anicet in Quebec (a rural site) collected in2006 were analyzed for their PAC content. In addition to the parent PAH, many alkylated-PAH, oxygen, sulphur and nitrogen heterocyclic analogues of the parent PAH were detected. Many of the PAHs observed at these sites were also found in diesel exhaust.