An electroanalytical investigation of the polybithiophene (PBT) band structure has been performed through the study of the voltammetric response of redox systems like ferrocene (FeC(p)2) and p-benzoquinone (p-BQ) at Pt/PBT working electrode. The FeC(p)2 response suggests a semiconducting behavior of the PBT polymer and the p-BQ voltammetric response can be used to indirectly test modifications of the polymer band structure occurring when the polymer is overoxidized; in particular the presence of states in the middle of the bandgap can be inferred.