The glassy state of matter is the amorphous state of the material most commonly formed by rapid cooling of the liquid below the glass transition temperature 𝑇𝑔. Such disordered system is not in a state of thermodynamic equilibrium, and with respect to the minimum energy, all degrees of freedom are not optimized. The absence of long-range translational and rotational symmetry leads to the appearance of many interesting physical phenomena such as the boson peak. If these systems are paramagnetic or if they are doped with paramagnetic centres, it is possible to study them using the electron spin resonance (ESR) method in which the influence of the spin dynamics of the nuclei of the observed material on the electron spin can be detected as a phase decoherence of electron spins. Using specific pulse sequences in ESR experiments, we have studied the differences between spin dynamics of glassy and crystalline realization of the same material. The aim of our work is to contribute to the understanding of the influence of the disorder on the dynamic effects observed in glass at low temperatures but not in the crystalline state, for which a theoretical description has not been agreed upon yet. Using various pulse techniques and focusing on a constant-time version of the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequences, we have studied two model systems: ethanol doped with nitroxyl radical TEMPO and 𝛾-irradiated trehalose. Both materials were studied in glassy and polycrystalline state at temperatures 𝑇≤20 K which correspond to temperatures 𝑇≤0.2 𝑇𝑔. In this temperature interval, molecular dynamics responsible for the relaxation of the spin system into thermodynamic equilibrium is the libration of molecular segments and quantum-mechanical tunnelling. Using dynamic decoupling of hyperfine interaction of electron spin with matrix proton spins, we studied the influence of disorder of molecular packing on spin dynamics. In the case of ethanol, nuclear spectral diffusion (NSD) proved to be a dominant mechanism of the phase decoherence of electron spins. However, in the case of trehalose, along with NSD, we have detected additional relaxation mechanisms, instantaneous diffusion, which prevents a direct conclusion about the influence of disorder on spin dynamics because it interferes with NSD in the phase decoherence of electron spins. The obtained experimental data are the basis for further theoretical studies of the molecular dynamics models in a disordered material since dynamic properties of nuclear spins (NSD), which are detected through the hyperfine interaction, directly reflect dynamic properties of the observed material.