The presented study deals with the structural and spectral properties of two derivatives of 2-thiohydantoin employing experimental and theoretical methods. The crystal structures of two novel cycloalkanespiro-5-(2-thiohydantoins) are described and compared with the available data on their dithio- and dioxo-analogues. For cyclopentanespiro-5-(2-thiohydantoin) – compound 1, two independent molecules are present in the asymmetric unit in contrast to its dithio-analogue. Cyclohexanespiro-5-(2-thiohydantoin) – compound 2, crystallizes as a monohydrate similarly to the dioxo-analogue. The cyclopentane rings in 1 adopt envelope conformation, while the cyclohexane ring in 2 adopts chair conformation. Although that the molecules of 1 and 2 possess same proton donor and acceptor groups, the presence of the crystallization water in 2 leads to different hydrogen bonding types and patterns. In compound 1 NH⋯O and NH⋯S intermolecular hydrogen bonds are formed, while the intermolecular hydrogen bonds in compound 2 are of OH⋯O, OH⋯N and NH⋯S types.The performance of quantum chemical methods, HF and DFT, to predict the molecular structure of the studied compounds, 1 and 2, and their dithio- and dioxo-analogues is assessed in comparison with available crystallographic data. Detailed analyses of the vibrational frequencies and the 13 C NMR shifts are performed with regard to the effect of the sulphur atom on the structural and spectroscopic properties of the studied hydantoin derivatives.