Free radical properties of synthetic pheomelanins derived from different cysteinyl precursors and eu-/pheo-copolymers have been investigated by electron paramagnetic resonance spectroscopy. g-Factors, lineshapes and intensities of the melain EPR spectra, were determined. The influence of microwave power on the intensities of EPR spectra was studies. Complex EPR spectra with hyperfine splitting are characteristic of all the studied samples. EPR spectra of mixed type - melanins are dominated by eumelanin single-line components. Paramagnetic centres with g-values from 2.0051 to 2.0056 occur in cysteinylDOPA- and cysteinyldopamine-melanins. Cooxidation of DOPA or dopamine and their 5-S-cysteinyl derivatives results in lowering g-factors to 2.0037-2.0046. Higher intensities were observed for EPR spectra of cysteinylDOPA-melanins compared to cysteinyldopamine-polymers. Slow spin-lattice relaxation processes are evident for unpaired electrons in the studied melanins.