In the last several decades, polycyclic aromatic hydrocarbons (PAHs) have been the subject of extensive investigation due to their presumed abundance in the interstellar medium (ISM). My thesis concentrated on investigating the dissociation of ionized PAH molecules in the gas phase under similar conditions of the ISM. The twelve PAHs studied were naphthalene (NAP), anthracene (ANT), phenanthrene (PHN), cyclopenta[d,e,f] phenanthrene (CYC), pyrene (PYR), fluoranthene (FLN), perylene (PER) and coronene (COR). In addition, two dihydro PAHs were studied to examine potential intermediates in H2 catalysis, 1,2-dihydronaphthalene (DHN) and 9,10-dihydrophenanthrene (DHP), and two stabilized fragments of PAHs, acenaphthylene (ACE), fluorene-H (FLU). These ions were studied using atmospheric pressure chemical ionization (APCI) to generate the ions and the fragmentation was produced by collision-induced dissociation (CID). The CID experiments were done at different lab frame collision energies to produce breakdown curves for all fragments in each molecule. These curves were fitted by using Rice – Ramsperger-Kassel- Marcus (RRKM) theory to derive the activation energy (E0) at 0K and the entropy of activation (∆‡ S) for each reaction. The primary dissociation channel observed was H loss and this fragmentation channel was a common fragment to all PAHs molecules studied. Also, there were other fragments (CH3, C2H2, C4H2) observed in all of these molecules studied except perylene and coronene. The final step in this project was to compare these results with results derived from imaging photoelectron photoion coincidence spectroscopy (iPEPICO) reported by West and co-workers in order to determine the suitability of the APCI-CID technique for deriving reliable kinetic parameters for this class of ions.