A short account of the spectroscopic studies dealing with various aspects of thione-thiol tautomerism in N-containing heterocycles is presented. The state of tautomeric equilibrium in solvents with different polarity is investigated and spectral characteristics of pure thione and thiol forms in the case of 2-pyridinethione and related compounds are evaluated. The recently observed reversible thione-disulfide transformation in water is also reported. The complex equilibrium in water is discussed and the influence of polychromatic UV-light on these potentially tautomeric systems and their symmetrical disulfides is also studied. The results of computational semiempirical and ab initio studies about the relative stability of tautomeric structures in gas-phase and in solvent environment are discussed.