We have performed solid state H-2 NMR spin-lattice relaxation measurements on perdeuterated benzene in the zeolites Na-X and Na-Y over the temperature range 155-350 K. The resulting NMR correlation times exhibit Arrhenius temperature dependence, with the following Arrhenius parameters : tau(0)(Y) = (9.6 +/- 0.4) x 10(-13) s, E(a)(Y) = 23.5 +/- 0.9 kJ mol(-1), tau(0)(X) = (8.8 +/- 2.3) x 10(-12) s, and E(a)(X) = 14.0 +/- 0.6 kJ mol(-1). This significant enhancement of benzene mobility from Na-Y to Na-X is reproduced with atomistic molecular mechanics simulations, yielding E(a)(Y) = 35 kJ mol(-1) and E(a)(X) = 15 kJ mol(-1), in quite reasonable agreement with the NMR measurements. We propose a simple length scale model which accounts for both the mobility enhancement and its order of magnitude. We find that the enhancement from Na-Y to Na-X is due to attractive interactions from S-III sites influencing adjacent S-II sites, making mobility more energetically favorable in Na-X. The relative magnitudes of our calculated hopping activation energies suggest that, while intracage and intercage benzene mobilities are comparable in Na-X, intracage mobility is much more rapid than intercage migration for benzene in Na-Y.