The effect of inorganic electrolytes on the determination of relative permittivity and concentration of water solutions of 1,4 dioxane was studied in this work. The method used was dielectrimetry, and NaCl, KCl, CsCl and LiCl at various concentrations were tested electrolytes. The interfering effect of these electrolytes was found for concentrations above 0.05 mmol l-1. It was also found that the interfering factor is purely the solution conductivity independent on the ion kind. The measurements were carried out with both the planar and the tubular detection cell having the electrodes insulated from the solution. The cell was connected to the differentiator (the voltage is the analytical signal) or multivibrator (the frequency is the analytical signal). A good agreement between experimental results and the modeled calculation for the detector with differentiator was also obtained.