Calculations are reported on the gas phase structures and tautomeric preferences of the reduced or leuco forms of 1,4-dihydroxy- and 1,4-diaminoanthraquinone using both the AM1 method and the 3-21G basis set. The results show that 2,3-dihydro-9,10-dihydroxy-1,4-anthraquinone is preferred in the former case and 1,4-diamino-2,3-dihydro-9,10-anthraquinone in the latter, in line with experimental data recorded in chloroform. The same pattern emerges when the calculations are simulated in water using the COSMO method, though the energy differences among the four possible tautomers of leuco-1,4-dihydroxyanthraquinone are reduced while those for leuco-1,4-diaminoanthraquinone increase.