The occupancy of C 2 and S 6 sites by Eu 3+ ions in nanocrystalline powders and microcrystalline ceramics of Lu 2 O 3 prepared from these powders was studied by Mössbauer spectroscopy. It was proved that in nanopowders prepared by vigorous combustion syntheses the occupancy of the C 2 and S 6 sites by Eu 3+ is almost random, with only a very limited preference for the former. For ceramic specimens formed at 1750 C within a few hours, it was found that Eu 3+ ions strongly prefer to enter the Lu 2 O 3 host at the C 2 site. We concluded that thermodynamically the non-centrosymmetric site C 2 is preferred to the S 6 site by Eu 3+. However, if the formation of crystallites is very fast, like in combustion syntheses, the Eu 3+ ions are entrapped into the two sites nearly randomly.