Rare earths(III) fluorides (LnF 3) are known to be amphoteric. Neodymium(III) fluoride reacted with SbF 5 in anhydrous hydrogen fluoride (AHF) to form very soluble Nd(SbF 6) 3 [1]. On the other hand LnF 3 behave as acceptors of F − in the presence of moderately strong fluoro base e.g. XeF 6 [2]. Our recent research was done in the systems LnF 3/AsF 5-HF and LnF 3/BF 3-HF. In the first system the compounds of the type LnF 3·2AsF 5 were obtained. They are very soluble in AHF saturated with AsF 5. From their IR spectra it can be seen that the symmetry of AsF 6 - is lower than octahedral. In the system LnF 3/BF 3-HF series of the compounds of the type LnF 3·nBF 3(n=1,2) were obtained. Their solubility in AHF saturated with BF 3 is much lower than in the case of LnF 3·2AsF 5. On the basis of vibrational spectra of LnF 3·nBF 3 it can be concluded, that the compounds are not typically ionic and the tetrahedral structure of the anionic part is deformed. The compounds of the type LnF 3 , AsF 5 are possible to be obtained from analogous compounds of the type LnF 3·BF 3 in AHF. The superior fluoride ion affinity of AsF 5 relative to BF 3 was used for the Lewis acids exchange. The effect of different types of LnF 3 structures (LaF 3 and YF 3) on the formation of different types of compounds will be discussed.