The results of investigation of a change of molecular mobility in sequential and simultaneous curing of the compositions based on epoxy and allylic oligomers are given, using the pulse NMR spectroscopy method. It was established that by simultaneous formation of epoxy and allylic networks the mutual hindrances to the full conversion of reactive groups occur resulting in the increase of defects in the interpenetrating polymer network (IPN) structure and an increasing molecular mobility of all its fragments. In the case of polymerization of allylic component of the IPN, when the formation of epoxy network is basically fully completed, the increase of molecular mobility in the system is due to a decrease of the limit conversion degree of polymerizable groups in the allylic monomer.