The crystal structures of the R 3 CuSnSe 7 (R = La, Ce, Pr, Nd, Sm, Gd, Tb and Dy) compounds (La 3 CuSiS 7 structure type, space group P6 3 , Pearson symbol hP24) were determined by means of X-ray powder diffraction: a = 1.07211(1)nm, c = 0.62770(1)nm, R I = 0.0613 (La 3 CuSnSe 7 ); a = 1.06310(2)nm, c = 0.62562(1)nm, R I = 0.0737 (Ce 3 CuSnSe 7 ); a = 1.05613(4)nm, c = 0.62532(3)nm, R I = 0.0964 (Pr 3 CuSnSe 7 ); a = 1.05002(4)nm, c = 0.62523(2)nm, R I = 0.0808 (Nd 3 CuSnSe 7 ); a = 1.03809(2)nm, c = 0.62848(2)nm, R I = 0.0745 (Sm 3 CuSnSe 7 ); a = 1.02435(2)nm, c = 0.63409(2)nm, R I = 0.0834 (Gd 3 CuSnSe 7 ); a = 1.01894(2)nm, c = 0.63642(2)nm, R I = 0.0881 (Tb 3 CuSnSe 7 ); a = 1.01359(3)nm, c = 0.63809(3)nm, R I = 0.0916 (Dy 3 CuSnSe 7 ).