Аннотация:The crystal structure of 2-hydroxy-4-methylbenzenesulfonic acid salts С6Н3(СН3)(ОН)SO3−М+ where М+ = NH4+, K+, Rb+ and Cs+ has been determined by X-ray diffraction method at 150 K. All salts are characterized by the same space symmetry group P 21/c, Z = 4 (Final R is 0.0382, 0.0309, 0.0272 and 0.0288 respectively). The С6Н3(СН3)(ОН)SO3−anion is in a common position as well as ammonium and alkali metal cations. In the crystal structure of each salt a rather weak hydrogen bond С–SO3−…НО–С is formed between the ОН group and the oxygen atom of the sulfogroup belonging to the neighboring C6H3(CH3)(OH)SO3− anion. Polycrystalline samples С6Н3(СН3)(ОН)SO3−М+ where М+ = NH4+, K+, Rb+ and Cs+ and С6Н3(СН3)(ОD)SO3−М+ where М+ = ND4+, K+, Rb+ and Cs+ have been studied by ATR FTIR and Raman spectroscopy in the frequency range 50–4000 cm−1. It is proposed an assignment of the –SO3− group vibrational frequencies as well as of the OH and OD groups (for the internal and external vibrations). The anion site symmetry is C1, but the –SO3− local symmetry estimated by spectroscopic methods is nearly ∼C3V. The concentration dependence of the ν(ОН), ν(ОD), ν(NH) and ν(ND) contours on the content of hydrogen isotopes was analyzed by FTIR and Raman spectroscopy. Dependence of the ν(ОН) and ν(ОD) widths on a degree of isotopic H–D dilution is weak, which can serve as a sign of some disorder in the hydrogen atoms positions.