Commercial macroporous strongly acidic ion-exchange resin (Bayer UCP 118) in its acidic and Na+ forms and a resin/Pd composite were investigated by means of electron spin resonance (ESR) and pulse field gradient spin echo-nuclear magnetic resonance (PGSE-NMR) techniques, to determine their molecular accessibility to 2,2,6,6-tetramethyl-4-oxo-1-oxypiperidine (TEMPONE) dissolved in water and the molecular mobility of both TEMPONE and water inside their accessible domains. The paramagnetic probe and water itself occupy both the micro- and macroporous domains of the resin particles, among which a rapid exchange is observed.