The thiosemicarbazide and its R1R2N1─N2H─C3(═S)─N4R3R4 derivatives, depending on the substituents nature of the terminal nitrogen atoms, display properties of compounds that make up the basis for obtaining pharmaceuticals. The biological activity of substances of this category is consistent with their structure. In this regard, the synthesis and study of the structural features of the thiosemicarbazide derivatives are of both scientific and practical interest. The aim of the given paper was to determine the crystal structure of 2-(2-hydroxybenzylidene)-N-mtolylhydrazinecarbothioamide (I) by means of X-ray analysis. The crystal structure of the investigated compound is based on the centrosymmetric dimers formed by hydrogen bonds between NH groups and sulfur atoms of thiosemicarbazide fragments of the neighbouring molecules (Fig 1,2). The thiosemicarbazide fragment has cis-arrangement of nitrogen atoms relative to the central N–C bond. The substituents near the bonds of N1-C1 and N2-C2 adopt Econformation, which is observed in another thiosemicarbazones [1 - 4]. The fragment of A(S1N1N2N3С1C2) in the molecule is practically planar. The deviations of these atoms from their mean plane range from -0.15 to 0.07 Å, while the molecule as a whole is non-planar. The least-square planes of phenyl rings B(С3¸С8) and C(C9¸С14) are oriented with respect to fragment A by angels of 7.6 and 66.8°, respectively, whereas the angle between B and C is equal to 73.1° . In the crystal, the X-H...Cg (π -Ring) interaction (H…Cg < 3.0 Å, and γ < 30.0º) [3] is observed for C15-H15 bonds in molecules related by translation along [010] direction, where H…B and γ values are equal to 2.96 Å and 19.9º, respectively.figureFig. 1. The dimer formation in the crystal structure. Fig. 2. A fragment of the packing in the crystal structure