The simulation of the structure of aromatic and quinoid poly(isothianaphthene) (PITN) has been improved, by the synthesis of new model compounds. The C-13 NMR investigation confirms our previous results that the geometric structure of this low-band-gap conducting polymer shows a strong quinoid character. For the aromatic structure, 1,3-dithienylisothianaphthene and a series of disilylated isothianaphthene oligomers were synthesized. trans-3,3’-Bibenzo[c]thienylidene was prepared in order to model the quinoid structure. All these new model compounds simulate better neighboring S-atom effects, a structural feature which was not accounted for in the previously reported model compounds.