Polymeric transition metal chalcogenides have attracted much attention because of their possible properties directly derived from their peculiar structures. Compared with polyoxometalates, polythiometalate chemistry is still very young. We report here the syntheses, structural characterizations and electrical properties of the novel polythiometalates, {[W₃Ag₃S₁₂]·[La(DMAC)₅(H₂O)₃·(DMAC)₄]}_n 1 and {[W₈Ag₁₀S₃₂]·[M(DEF)₈]₂}_n(M = La 2 and M = Nd 3). The complexes were obtained by self-assembly of (NH₄)WS₄ and AgNO₃ with Ln(NO₃)₃ (Ln = La, Nd) in different solvents: DMAC (DMAC = N,N′-dimethylacetamide), DEF (DEF = N,N′-diethylformamide). The title compounds represent two novel structure types of W/Ag/S polythiometalates, 1: a single-stranded helix chain; 2 and 3 are isomorphous: equal step zigzag chains with a double square unit. The unusual 1 has two helices: an anion chain and a cation chain simultaneously exist in the unit cell and the anion helix is defined by a pitch (length per turn) of 17.65 Å, and a radius of circumscribed cylinder of 8.88 Å. Room temperature conductivities of 1, 2/3 are 1.16 × 10^–4, 2.58 × 10^–4 S cm^–1.