Novel applications of 2-mm ESR (frequency ~ 150 GHz, resonance field ~ 50 kG) to study of molecular dynamics of spin probes and spin labels are discussed. Experimenta approach includes motional line broademing vs. motional line shift measurements as well as inspection of saturation transfer 2-mm spectra of nitroxide spin probes. High resolution of 2-mm spectra enabled to choice between different models of molecular reorientation while saturation transfer experiments indicated new type of relative motion competing with the whole body rotation of molecules.