The structures, vibrational frequencies and adiabatic ionization energies of HPCN and HNCP are calculated at several levels of theory. The adiabatic ionization energy of HPCN is found to be 10.16 eV at the G3 level of theory. The singlet state of HPCN+[Formula: see text] is found to be approximately 1.3 eV below the lowest energy triplet state (ã3A ″). Both states have a bent equilibrium molecular geometry. The adiabatic ionization energy for HNCP is calculated to be 8.30 eV at the G3 level of theory. In contrast to HPCN+, the triplet state [Formula: see text] of HNCP+is lower in energy than that of the singlet state (ã1A ′) by approximately 1 eV. Also, the triplet state of HNCP+is linear in contrast to that of HPCN+due to the larger interaction between neighboring 2p orbitals on the central atoms in HNCP+relative to the interaction between the 3p and 2p orbitals on the central atoms in HPCN+. Simulated photoelectron spectra (PES) are presented for the transitions producing both the singlet and triplet ion states of both isomers. As predicted by the dramatic geometry change in the case of [Formula: see text], there is a long progression in the bending mode of the cation in the simulated PES.