Rotating frame H-1 n.m.r. spin-lattice relaxation times T-1 rho have been used to study relaxation processes in partially crystalline polypropylene and polypropylene modified by a copolymer of ethylene and alkylaminoacrylate. Measurements were carried out within the temperature range of 250-420 K. Three relaxation times T-1 rho were detected over the whole temperature range. alpha(c) relaxation in the crystalline regions of the polymer, relaxation processes beta(U) and beta(L), associated with an apparent double glass transition, and alpha(a) relaxation process, which was ascribed to a free reorientation of the whole chains in the amorphous regions, were observed by temperature dependences of these relaxation times. In addition to the alpha(c) relaxation, another relaxation process with relatively low molecular mobility was found in crystalline regions. The influence of the polymer modifier on the observed relaxation processes greatly depends on its amount.