AbstractAdvanced solid‐state NMR techniques exploiting1H spin diffusion are described, which rely on selecting1H magnetization of one of the components on the basis of1H chemical shift or mobility differences under multiple‐pulse irradiation. To monitor the progression of1H spin diffusion, the higher resolution of13C CP MAS spectra is exploited for NMR detection. For evaluation of the data, full quasi‐analytical solutions of the diffusion equation as well as initial‐rate approximations are derived, applied and discussed. In order to obtain quantitative results, the1H spin‐diffusion constant has to be determined. To this end, the domain sizes in poly(styrene)‐poly(methyl methacrylate) systems including symmetrical diblock copolymers have been measured. The comparison of the NMR results with SAXS and TEM data yields the spin‐diffusion coefficient for PS and PMMA. The resulting value ofD=0.8 nm2/ms is expected to be typical for rigid organic systems. The domain sizes investigated range from approximately 1 nm