Résumé : This paper summarizes our efforts to design and develop a new instrument for measuring the diffusion coefficients in binary and ternary mixtures based on Taylor dispersion technique. The main task was to build a relatively simple instrument with reasonable accuracy which can be applied to a wide range of systems. Previous studies of the diffusion in ternary liquid mixtures were focused at electrolytes and diluted solutions. The mathematical approach was also developed for such kind of systems. We adapted the existing approach for non-dilute mixtures using mass fractions instead of molar concentrations. The experimental protocol and algorithm for the diffusion coefficients extraction were validated against the literature data for the binary system water/isopropanol. We report the results of the measurements of diffusion coefficients in symmetric point (1:1:1) of ternary mixture THN/IBB/C12.