The 3- and 4-ring polycyclic aromatic hydrocarbons (PAHs) are the most abundant of PAHs in air particulate matter (PM). Thus we have investigated heterogeneous oxidation of 3- and 4-ring PAHs in a small-scale flow reactor using quartz filter as a support. Four representative PAHs, anthracene, phenanthrene, pyrene, and fluoranthene, were exposed to either NO2, O3 or NO2+O3 (NO3/N2O5) with a goal to identify and attempt quantification of major product distribution. A combination of gas chromatography with mass spectrometry (GC–MS) with/without derivatization and liquid chromatography with high resolution MS (LC-HRMS) was used for identification. For the first time, a comprehensive characterization of a broad range of products enabled identifying ketone/diketone, aldehyde, hydroxyl, and carboxylic acid PAH derivatives. Exposure to NO3/N2O5 (formed by reacting NO2 with O3, a more powerful reactant than either O3 or NO2) produced additional compounds not observed with either oxidant alone. Multiple isomers of nitrofluoranthene and, for the first time, nitrophenanthrene were identified. In addition hydroxy-nitro-PAH derivatives were observed for the reaction of anthracene with NO3/N2O5. Monitoring of specific common ions such as those of 176 and 205 m/z attributed to carbonyl phenanthrene and deprotonated phenanthrene ions respectively was shown to be a useful tool for identification of multiple pyrene oxidation products