The effect of the chemical structure in the electrical response (membrane potential, Delta phi, salt diffusion, D-s, resistance, R(m), and capacitance, C-m) of two new aliphatic-aromatic polyamide membranes is considered. They are poly(ether-amide)s with an oxygen atom difference. Measurements were carried out with NaCl and MgCl2 solutions at different concentrations. Equivalent circuits were determined by impedance spectroscopy and a parallel R(m)C(m) association was obtained for both membranes and electrolytes. Under identical external conditions, significant differences for the membrane resistance values were found as a function of the membrane chemical nature, but the capacitance hardly depends on both membrane and electrolyte. From Delta phi and R(m) values some membrane characteristic parameters such as transport numbers and ionic diffusion coefficients were determined. Concentration dependence of all these parameters was also studied.