The abatement of volatile organic components (VOC) in emissions is an extremely stringent environmental problem. One of the most frequently used technologies is the regenerative thermal oxidation (RTO), because of its thermal efficiency and cost-effectiveness. In the present paper, a computational one-dimensional unsteady model, able to account for fixed as well as fluidized beds of particles, is developed, validated, and applied to realistic plant conditions. Process thermal efficiency and gas pressure drop are calculated as functions of the system geometry and operating parameters. Results of a validation against experimental data are presented first, showing very good agreement. The overall thermal efficiency is obtained as the performance index for packed beds of spheres and Rashig rings and fluidized beds of spheres, allowing a direct comparison of the two systems. The simulation results clearly show that, despite the high efficiency of gas-solid contact in fluidized beds, their thermal performances are unacceptably poor, because of the cyclic nature of the process.