Conjugated bi- and terthiophenes have been substituted by cyano groups on several positions of the oligothiophene backbone. Their ability to form, after oxidation, longer oligothiophenes has been analyzed by electropolymerization. Whereas cyano-substituted bithiophenes and dicyanoterthiophenes were found to be unable to give longer products, monocyanoterthiophenes could be dimerized, leading to disubstituted sexithiophene derivatives. The electrochemical and optical behavior of the three new electrosynthesized dicyanosexithiophenes were studied and compared with those of shorter substituted cyano-oligomers.