1,3,8-Trihydroxynaphthalene is one of the substrates in the fungal melanin biosynthesis pathway. We present theoretical studies on energies of its tautomeric forms and their rotamers. Several theory levels and solvent models have been tested using experimental results obtained in water-acetone mixtures as the reference point. Our results indicate that the best agreement with these data is obtained with density functional theory levels when the continuum solvation model uses the united atom topological cavity. We also noticed a fairly good performance of the semiempirical AM1 method that makes it a promising alternative for studies of large systems.