Density functional theory (DFT) calculations on SNS, S2N2, and S4N2 are reported. Both local and gradient-corrected nonlocal density functionals are used with moderate and large basis sets. The relative energies, structural parameters, and vibrational frequencies are reported for each molecule and compared with the experimental and theoretical data available in the literature. For S2N2, DFT results predicted the order of stability of the three low-energy structures as linear chain < pairwise ring < alternate ring in contrast to the MP2 results but in agreement with MRCI results. For S4N2 the order of stability is found to be (1,3) isomer < twisted form of (1,4) isomer < chair form of (1,4) isomer. We discuss identification of experimentally observed infrared absorption peaks of S2N2 and S4N2.