Two series of hydrated ¯uorides have been prepared by a ``chimie douce'' process. For the ®rst family, more than twenty ®ve compounds of d-ALn 3 F 10 ,xH 2 O (A z ~alkaline ions, NH 4 z , H 3 O z and Ln~lanthanide) have been prepared. They crystallize in the Fd3 Å m space group (a#15.4 A Ê and Z~16) and are isotypic with d-The diamond-type structure of these phases (diamond stacking of octahedral units of antiprisms, called UOA [8] ), creates cavities and tunnels where the water molecules can move.The second family, c-ThLn 2 F 10 ,H 2 O (Ln 3z ~Er 3z , Dy 3z and Yb 3z ) results from the substitution of Ln 3z and A z by a tetravalent cation. The new compound c-ThEr 2 F 10 ,H 2 O (Fm3 Å m space group, a~10.739(1) A Ê and Z~8) is isotypic with c-KYb 3 F 10 . Water molecules are located inside the tunnels (8c sites) of a CCP stacking of UOA [8] through which they can move.For both series, the thermal stability and the zeolitic behaviour, studied by DTA/TGA and X-ray thermodiffractometry, are reported and a low zeolitic water capacity, around 2±4% in mass, is observed.