Introduction The high water purity demanded by the power industry requires practically the removal of all the contaminantes - organics and anorganics - present in the water supplies available to generating plants. For the demineralization system to operate reliably and economically, the ion exchange resins must be in good condition. The efficiency of the water treatment plants for the power industry is achieved through a careful selection of the ion exchangers resins, used in for the demineralization process. The types of anion exchangers used for the anionic degrees in the demineralization lines were differentiated through their microstructure specific characteristics (gel, semi-porous, macroporous), their functional groups (primary, secondary, tertiary and quaternary amine) as well as through their tridimensional matrix (acrylic, styrene - DVB). This poster presents the research about the importance of the intern structure macroporous of the ion exchange resins (specific surface area, pore volume and pore size distribution) in the organic impurities adsorbtion and desorbtion processes. Results The organic impurities in water can be of complex colloidal type in varying ratio and will be adsorbed in the ion exchange resins, if these possess the special matrix with an additional system of larger pore channels. The type of ion exchange resins investigation was Amberlite (ROHM & HAAS CompanyFrance), Lewatit (Bayer Company – Germany) and Purolite ( Purolite – Romania Company). Even better evidence of porosity and surface properties was obtained through physical measurements of the pore volume, the pore surface area and the pore diameter with Carlo Erba Porosimeter Mod. 2000 equipment. In the mercury porosimetry method, the total volume of mercury that penetrates into the pores is measured as a function of pressure. At the smallest pressures, mercury can penetrate only into the largest pores, and the higher the pressure is the smaller are the pores which are filled. The total volume of penetrated mercury determines the volume of the pores with a radius larger than the radius corresponding to the pressure calculated with Washburn equation {P = - 2σ (P,T) cos Ө / Rp}. The continuous registration of the whole range of pore diameters from large to small values results in the integral pore distribution curves ( intrusion – extrusion curve). The interpretation of their shape and steepness allows to learn more about the range of the pore diameters and the predominant pore size. To select the macroporous ion exchange resins who have been the ″capture″ of the organics compounds in pores for demineralization of organically polluted raw water and to establish the physical characteristics.The morphological characteristics of macroporous ion exchange resins used for the demineralization of organically polluted raw watertabelThe technological experiments and the pore – structure investigations show that the basic structural properties are of great importance when choosing the ion exchange resins for the pure and ultrapure water production. Poster presents: mathematic equations, distribution curves, tables and structures.