The adsorption rate of NO was investigated for a single agglomerate of zeolite crystals. A mathematical model was set up to describe diffusion of gaseous NO within the void space of the agglomerate, adsorption and diffusion of adsorbed species inside the zeolitic crystal. The values of intracrystalline diffusivity and its activation energy were estimated by adsorption measurements with a tapered element oscillating microbalance (TEOM). The adsorption rate significantly decreased for the large agglomerate of low voidage due to the increase in the diffusion resistance inside the void space of the agglomerate. The results of the modelling investigation based on the experimental data revealed that the agglomerates of sizes in the range from 2 to 4 x 10(-3) M in diameter and of voidage in the range from 0.35 to 0.45 could be favorable for moving-bed applications from the viewpoint of adsorption.