Hybrid (organic/inorganic) gels are studied in terms of cyclohexane diffusion transients with an oscillating balance reactor (OBR) which, unlike conventional microbalances, has the well-defined gas flow profile characteristics of packed beds (PB's). The OBR-based flow-through adsorption system, when properly designed, has very good time resolution and is particularly useful in modeling adsorption processes under more realistic PB geometries. With the test sample adopted in this study, the "semirigid" nature of hybrid gels becomes apparent when simple relaxation models are chosen to fit experimental data.