The "onium" hexafluorosilicates, in particular, ammonium hexafluorosilicate (NH4)2SiF6 and hexafluorosilicates of amino acids represent in the recent years the objects of intensive research as compounds possessing by the caries-protected and hyposensitive properties [1-3]. In present communication we describe some results of synthesis and physico-chemical investigations of three new salts with antibacterial cations – (CH)SiF6, (PHMG)(SiF6)1.5 and (CP)2SiF6 (CH – chlorhexidine, PHMG – polyhexamethylene guanidinium, CP – cetylpyridinium). The compounds with the composition (CH)SiF6 (I), (PHMG)(SiF6)1.5 (II) and (CP)2SiF6 (III) where obtained by the interaction of corresponding “onium” chlorides in methanol solution with fluorocomplex acid H2SiF6 (45 %) in mole ratios 1 : 3 [4]: 2(L)Cl (MeOH) + H2SiF6 (aq) → (L)2SiF6 + 2HCl. Reaction products I – III where isolated in an approximately qualitative yield. All compounds were characterized by elemental analysis, IR, NMR 19F and mass-spectrometry. Mass spectra (EI) of I – III are contained the peak of ion [SiF3]+ (m/z = 85) – characteristic product of fragmentation of SiF4. According to IR spectroscopy data, “onium” hexafluorosilicates I – III have ionic structures. The vibrations of the groups ν(NH), ν(N+H2) in the salts I and II appear as a strong absorption bands at 3360 – 3180 cm–1; δ(N+H2) vibrations appear at 1634 and 1637 cm–1. In compound III, three νring vibrations at 1638, 1577 and 1488 cm–1 are observed. The strong ν(SiF) and δ(SiF2) stretches of SiF6 2– anions are observed in their characteristic regions (at 744 – 734 and 482 cm–1 respectively). The NMR 19F spectra of compounds I, II (d-DMSO) and III (CDCl3) have one resonance at –136.70, –135.09, –133.8 ppm. The range of chemical shifts observed could be due to changes in sample concentration, different solvents, the presents or absents of water, and the differing cationic species. The results of thermogravimetric analysis are consistent with a multi-stage thermolysis scenario for hexafluorosilicates I and II. The temperatures of thermolysis beginning of the complexes I and II are 270 and 100 °C, respectively. The studied compounds I – III are characterized by the predicted high tendency to hydrolysis in dilute aqueous solutions with the formation of silica and fluoride anion that allows considering these salts as potential cariesprotected agents. The study of biological activity of these compounds is the subject of further investigations.