Crystals of 4-cyanophenyl 1,5-dithio-β-d-xylopyranoside S-5 oxide (1) and 4-ethyl-2-oxo-2H-1-benzopyran-7-yl 5-thio-β-d-xylopyranoside S-5 oxide (2) are monoclinic, space group P21, with two independent thioxylosides molecules in the asymmetric unit. The unit cell dimensions are α = 26.385, b = 5.934, c = 8.902 Å, and β = 109.90 ° for 1 and α = 16.033, b = 16.676, c = 6.459 Å, and β = 91.26 ° for 2. The present work provides structural information on the influence of substitution of intracyclic and glycosidic oxygen atoms by sulfur atoms, as well as on the influence of aromatic rings and of sulfoxide groups on the carbohydrate moiety. In both molecules, the xylopyranosides rings have the classical4C1 conformation. For 1, the orientation of the phenyl substituent with respect to the xylopyranose is very similar in the two independent molecules: the φ and ψ torsion angles are respectively: (−99.5°, 153.8°) and (−102.1°, 154.2°). This is not the case for 2, for which these values are strikingly different: (− 79.4°, 172.1°) and (− 130.2°, −178.4°). In each structure, the molecules are hydrogen bonded within a network of infinite chains.