Dielectric properties of four diols having different chemical structures of the hydrophobic part were determined by the time domain spectroscopy method in the frequency range from c. 15MHz to c. 7GHz. The static permittivity clearly reflects the changes in the position of the dipole moments in the molecules. The dielectric relaxation times characterizing the diol part of the molecules are similar for all the substances studied. In the case where the phenylthiadiazole unit is built into the alkyl chain, two well separated processes were observed: one connected with the ‘hydrophobic’ and the second with the ‘hydrophilic’ part of the molecule. This emphasizes the amphotropic character of such molecules.