Quasielastic neutron scattering (QENS) and NMR pulsed field gradient spin-echo (PGSE) techniques have been applied to three types of sedimentary rocks, in order to monitor the diffusion process through the measurement of the diffusion coefficient D(t) of the water trapped into the rock pores. As it is expected for restricted diffusion,D (t) is found to decrease by increasing the diffusion time, starting from the free water value D 0 at t → 0 down to an asymptotic valueD ∞ . From the behavior D(t) versus t, geometrical and physical properties of the rocks are deduced.