The properties of a good polarized target material are high number of polarizable nucleons compared to the total amount of nucleons, high polarization degree, short polarization build up time, slow polarization loss rate in frozen spin mode, good resistance against radiation damage and easy handling of the target material. For the dynamic nuclear polarization the material has to be doped with free radicals. Two different ways are usual: chemical doping by mixing with free radicals and creation of F-centers by irradiation in an intensive electron beam. Commonly used target materials are butanol, ammonia, lithium hydrides and their deuterated counterparts. A very interesting material is hydrogen deuteride, because it has the maximal content of polarizable nucleons. High proton polarizations have been reached in a large naphthalene single crystal using optically excited triplet states of fully deuterated pentacene guest molecules. at temperatures around 100 K and magnetic field of 0.3 T. Hyperpolarized carbon-13 has been studied for medical imaging applications