Geometric and electronic structures of linear SMnS, cyclic eta(2)-MnS2, and linear eta(1)-MnS2 isomers of MnS2-, clusters have been investigated with B3LYP, CCSD(T), and NEVPT2 methods. The ground state of the anionic cluster is determined as (5)Pi(g) of the linear SMnS- isomer, while the ground state of the neutral cluster May be either the (4)Sigma(-)(g) of the same isomer or the (6)A(1) of the eta(2)-MnS2 cluster. The experimental photoelectron spectrum of the MnS2- cluster is interpreted by contributions of these two isomers. The-high-intensity band at a binding energy of 2.94 eV is attributed to the (5)Pi(g) --> (4)Sigma(-)(g) transition between the linear SMnS-/0 clusters. The lower energy feature in the Spectrum at binding energies between 1.9 and 2.3 eV and exhibiting a:low intensity, is ascribed to electron detachments Within the less stable eta(2)-MnS2-/0 clusters. Ionizations from the lowest energy (7)A(1) state of this isomer to the neutral (6)A(1), (6)A(2), (8)A(2), and B-6(2) states are responsible for this part of the spectrum. The extreme low intensity part between 1.3 and 1.9 eV can be due to excited states of,either SMnS- or eta(2)-Mn-2(-).