A reading of the main phonological works of the Prague school on one side and ofTheory of Languageand other writings by Bühler on the other, shows, in the Author’s perspective, that despite some superficial correspondences, the concept of phoneme in the Prague school (and therefore in classical structuralism) is deeply different from that of Bühler, who integrates it in a physiognomic model reducing its relevance. Furthermore, the article points out that Troubetzkoy’s standpoint towards the heritage of Baudouin de Courtenay is dissimilar from that of the Prague School.