This paper reports the results obtained by studying the structure of activated composite membranes (ACM) containing organophosphorus extractants as carriers. The porous structure of membrane samples containing different concentrations of di(2-ethylhexyl)phosphoric acid (DEHPA) and di(2-ethylhexyl)-dithiophosphoric acid (DTPA) from 0 to 7×10-3 mmol·cm-2 was characterized by gas adsorption method (BET). The results obtained by the BET technique indicate that both the total pore volume and the specific surface area of ACM samples decrease with the concentration of the carrier in the casting solution. The carrier in the membrane is mainly located in pores having large and medium diameters. The chemical structure of the carriers studied does not influence their distribution in the ACM. These results correlate well with those obtained by using different spectroscopic techniques to evaluate the properties of ACM samples. Thus, a quantitative correlation has been obtained between the carrier content in the membrane and its initial concentration in the modifying solution for both organophosphorus extractants studied by using the ICP technique. Dependencies of this type can serve as a sort of calibration curve to prepare ACM samples with a desired carrier content. X-ray microanalysis (EDS) was used as a nondestructive method for determination of carrier concentration in ACM. Both EDS and impedance spectroscopy (IS) methods were applied to evaluate the changes of internal membrane structure in the course of preparation of ACM samples with different carrier content.