The paper informs about the possibilities of studying the path‐ways of photolytically induced radical formation and of the first steps of radical reactions by methods of magnetic resonance. The investigations were carried out on initiator systems for laser induced polymerization containing anthraquinone. triethylamine and erythrosine in various solvents. The applied methods were time‐domain and steady‐state cw‐ESR, electron spin echo (ESE), 1H NMR and stimulated nuclear polarization (SNP). The chemically induced polarization of electron spins and nuclear spins (CIDEP and CIDNP) and their relaxation was used as main source of information about the fast laser—induced reactions.