Titanium(IV) oxide/polydimethylsiloxane (PDMS) and calcium carbonate/ PDMS composite powders were obtained by adsorption of the polymer from a chloroform solution onto the inorganic particles followed by a thermal treatment. The composites were characterized by H-1-NMR relaxation and porosimetry. The composites present shorter spin-lattice (T-1) and spin-spin (T-2) proton relaxation times than silica-reinforced PDMS, and the activation energies for the motions that cause spin-lattice relaxation are 5.8, 4.9, and 0.72 kJ mol(-1) for TiO2/PDMS, CaCO3/PDMS, and neat PDMS, respectively, revealing the greater rigidity of the polymer chains within the composite. Spin-spin relaxation (T-2) measurements of the composites showed a major component with a shorter T-2 and a minor component with a longer T-2. The intensity ratio of these two components is very close to the ratio between the amount of polymer that remains between the particles and that penetrating the particle pores as measured by Hg intrusion porosimetry. The shorter T-2 component was thus assigned to polymer interspersed among the particles, while the longer T-2 component was assigned to polymer within the particle pores.