Perfluorinated cation-exchange flat-sheet membranes were treated with ethylene diamine (EDA) to investigate the influence of EDA-surface-treatment on the process of platinum deposition on these membranes. Electroless chemical deposition of Pt particles on modified membranes was achieved using the Takenaka-Torikai method. Chemical modification of the surface, a profile of platinum distribution within the membrane, platinum particle size, and chemical structure of the membrane were investigated by means of electrical conductivity measurements, scanning electron microscopy (SEM), and IR-spectrometry. Dielectric analysis (DEA) was used to investigate the dipole and ion mobility of hydrolysed EDA-treated membranes.