Benzoquinone (BQ), deuterobenzoquinone (d 4 -BQ), and hydroquinone (BQH 2 ) are investigated in ethylene glycol by means of direct detection fast time-resolved EPR spectroscopy after laser flash photolysis. The development of the magnetization as a function of time and magnetic field is obtained and analyzed in terms of the Bloch equations and hyperfine parameters. The signals are attributed to the semiquinones BQH • and d 4 -BQH • . The presence of 1,2-dihydroxyethyl radicals during the photolysis of BQ and d 4 -BQ is verified. No alkyl radicals are observed in solutions of BQ with excess BQH 2 . Detailed analysis of the chemically induced dynamic electron polarization spectra with respect to their development in time shows that polarization patterns of the semiquinones can be traced back to a superposition of triplet mechanism and radical pair mechanism, the latter arising from geminate T-pairs. Hence, two independent pathways for polarization are assumed: reaction of triplet benzoquinone with ethylene glycol leads to the semiquinone and dihydroxyethyl radicals with all signals in emission, whereas the reaction of triplet BQ and BQH 2 yields two semiquinones exhibiting both net emissive and multiplet emissive/absorptive intensity distributions.