Hexamethylphosphoramide (HMPA) coordinated Sm(III) complexes containing different counter anions are isolated and structurally characterized by X-ray crystallography. These complexes are classified into the following four types: tricationic complexes [Sm(H 2 O) 4 (hmpa) 3 ]I 3 1 and [Sm(H 2 O) 5 (hmpa) 2 ]I 3 (hmpa) 2 2, dicationic complexes [SmCl(H 2 O) 4 (hmpa) 2 ]Cl 2 THF 3 and [SmCl(hmpa) 5 ][BPh 4 ] 2 4, cationic complex [Sm(OTf) 2 (hmpa) 4 ]OTf CHCl 3 5, neutral complex [Sm(OTf) 3 (H 2 O)(hmpa) 3 ] CHCl 3 6. Crystal data of these complexes are 1: monoclinic, space group P2 1 /c with a = 15.593(5) 9, b = 14.495(3) 9, c = 19.158(4) 9, β = 95.57(2)°, V = 4381(1) 4381(1) 9 3 Z = 4, R = 0.048, R W = 0.076; 2: monoclinic, space group Cc with a = 14.054(6) 9, b = 19.163(2) 9, c = 20.531(3) 9 V = 5129(1) 9A 3 , Z = 4, R = 0.062, R W = 0.067; 3: triclinic, space group P1 with a = 15.309(6) 9, b = 15.339(3) 9, c = 8.751(2) 9, α = 102.99(1)°, β = 103.05(3)°, γ = 107.36(3)°, V = 1813(1) 9 3 , Z = 2, R = 0.054, R W = 0.074; 4: monoclinic, space group P2 1 /a with a = 20.128(5) 9, b = 17.582(3) 9, c = 25.512(7) 9, β = 99.93(2)°, V = 8893(3) 9 3 , Z = 4, R = 0.048, R W = 0.052; 5: triclinic, space group P1 with a = 15.174(3) 9, b = 17.459(7) 9, c = 11.977(4) 9, α = 104.28(2)°, β = 102.65(3)°, γ = 90.40(3)°, V = 2994(1) 9 3 , Z = 2, R = 0.060, R W = 0.077; 6: triclinic, space group P1 with a = 13.440(3) 9, b = 14.975(6) 9, c = 12.655(3) 9, α = 90.95(3)°, β = 93.95(2)°, γ = 84.15(2)°, V = 2527(1) 9 3 , Z = 2, R = 0.071, R W = 0.091. The coordinative nature of these complexes is discussed on the basis of observed bond lengths and angles.Des complexes du Sm(III) coordines a l'hexamethylphosphotriamide (HMPT) et contenant divers contre-ions ont ete isoles et leur structure a ete caracterisee par diffraction aux rayons X. Ces complexes ont ete classes selon les quatre types suivants: complexes tricationiques [Sm(H 2 O) 4 (hmpt) 3 ]I 3 1 et [Sm(H 2 O) 5 (hmpt) 2 ]I 3 (hmpt) 2 2, complexes dicationiques [SmCl(H 2 O) 4 (hmpt) 2 ]Cl 2 THF 3 et [SmCl(hmpt) 5 ][BPh 4 ] 2 4, complexe cationique [Sm(OTf) 2 (hmpt) 4 ]OTf CHCl 3 5, complexe neutre [Sm(OTf) 3 (H 2 O)(hmpt) 3 ] CHCl 3 6. La nature des coordinations de ces complexes est commentee d'apres les longueurs de liaison et des angles observes.