This paper describes the preparation of the CNTs-based gas sensors, which are achieved by the utilisation of aqueous dispersions of carbon nanotubes (CNTs) using NaDDBS as a surfactant. The sensors are made of IDEs (Interdigitated electrodes) on which the CNTs dispersion are dropcast deposited. The sensing layers are characterized by Raman and IR spectroscopy as well as SEM analysis and electrical characterization (I-V). Finally, the sensor response and relative resistance change (ΔR/R) versus concentration under low NO2 gas concentrations are reported. The sensor performance is evaluated by focusing on the influence of the surfactant and the annealing process on the final sensor. The effect of the surfactant has been investigated in order to establish the optimal conditions for the realization of the sensors using dispersion route. Although the use of surfactant provides stable dispersions, the annealing treatment of the sensor before sensing experiments need to be correctly tuned for good sensor performance. Indeed, even if the presence of surfactant does not drastically hinder the sensor response, a major problem comes from its residue after decomposition under certain annealing conditions (≥300 °C). In fact the surfactant residue seems to obstruct active sites on the sensor surface and therefore render the sensor unusable. Lower annealing conditions (≤150 °C) seem to be the optimum.