Computations are reported for the cumulenethiones H2CnS (n = 3-9). The structures, harmonic frequencies and the dipole moments are computed using the density functional theory and the MP2 methods. Most of the spectroscopic properties of these molecules are reported for the first time. The carbon skeletons in the lowest energy structures of these molecules are found to be linear (C-2v symmetry), but very floppy. Several conformers of H2C3S and H2C4S with bent or cyclic carbon-sulfur skeleton are also predicted.