The sensitivity and explanation capability of EPR spectroscopy was proved to increase considerably at 2-mm waveband. The present report summarizes the basic aspects of an investigation at 2-mm waveband EPR of magnetic, relaxation and dynamics parameters of various low-dimensional solid-state organic semiconductors with mobile paramagnetic impurities, e.g. polytetrathiafulvalene, polyaniline, fullerene complex. All components of g- and A-tensors of such paramagnetic centers were determined. The method of steady-state saturation of spin packets was used for determination of relaxation and diffusion rates for paramagnetic centers with different mobility. The superslow anisotropic molecular dynamics in some conducting polymers was investigated by means of the saturation transfer (ST-EPR) method. It was shown that spin and charge transfer correlates with molecular dynamics. The mechanism of charge and spin transport in the systems under study was ascertained to depend on the doping level. Therefore, non-linear 2-mm waveband EPR spectroscopy allows one to obtain more additional information on spin relaxation as well as on spin, change and molecular dynamics in different low-dimensional semiconductors.