An overview of the main procedures for the preparation of fluorides with very high surface areas is given. Three processes are outlined: (i) plasma fluorination, (ii) sol–gel route and (iii) oxidative decomposition of inorganic precursors. From all three processes nanostructured metal fluorides with 100–400m 2 g −1 can be obtained. Prevention of the local overheating during fluorination seems to be the key factor to obtain the high surface area fluorides. TEM investigations of AlF 3 and CrF 3 obtained by oxidative decomposition revealed considerable differences in their morphologies and crystallinity. CrF 3 is completely amorphous and unstable under beam. AlF 3 contains an amorphous phase and nanocrystalline phases of α-AlF 3 and β-AlF 3 . Nanocrystals are uniformly distributed within the amorphous phase. Also present are the rod-like nanostructures that consist of β-AlF 3 and are 5–10nm wide.