The electrochemical behaviour of polyaniline (PANI) is particularly complicated, with respect to the other conductive polymers, in respect of the two reactions (protonation-deprotonation and oxidation-reduction) which occur simultaneously, but with different rates; the respective rates of the two reactions vary with the pH of the electrolyte. A further complication arises from the existence of three insulating forms with different oxidation levels. Raman, as well as optical spectroscopies are excellent tools to obtain an in situ identification of the polymer under polarization. However, it was observed that the connections between Raman/optical features and voltammograms are far from being straight. A more thorough analysis can be obtained using ＇resonant＇ Raman with several excitating laser lines, because each of these fines is able to enhance;the response of a selected polymer segment. The blue line was expected to lead to the localized polaron excitation, the red line to the exciton excitation and the near-IR line to the intrachain excitation. The use of red and IR lines brought a splitting of the C=N and C-N+ stretching modes, displaying the large variety of different segments existing at every potential. The broadening of the voltammograms obtained in weakly acidic media was easily understood; in very acidic solutions, on the contrary, owing to the sharpness of voltammograms, the complexity of the reactions arising in PANI during its polarization was not at all suspected. In the present work, PANI doped by functionalized sulfonic acids is studied.