To help future structural characterization of gaseous P2S2 by experimental techniques, accurate relative energies, geometries, rotational, and quartic centrifugal distortion constants, dipole moments, harmonic vibrational frequencies, infrared intensities, and vertical ionization energies have been determined from ab initio calculations for several isomers of P2S2. There are at least five minima identified on the lowest singlet potential energy surface of P2S2. The energy results obtained indicate that a PP-bridged bicyclic (butterfly-type) isomer of C-2v symmetry corresponds to the global minimum, while the planar cyclic 4-membered isomers of D-2h and C-2v symmetries are the second and third most stable isomers, respectively.