Powder X-ray diffraction data are reported for RE6UO12 (RE=Eu, Gd, and Dy). The powders were prepared by a solution combustion method using urea as fuel. All compositions exhibit a rhombohedral structure with hexagonal unit cell parameters of a=1.012 67 (9) nm, c=0.9601 (1) nm for Eu6UO12; a=1.008 78 (6) nm, c=0.954 24 (7) nm for Gd6UO12; and a=0.998 06 (7) nm, c=0.944 03 (8) nm for Dy6UO12. The diffraction patterns of all the compounds are indexed on the R3¯ space group with Z=3. The a and c values decrease with increasing atomic number of the rare earth ion.