The structures of tetra(m-methoxyphenyl)tin (1) and tetra(o-methoxyphenyl)tin (2) have been determined at 225 and 290K, respectively. Crystal data : (1), m.p. 361.5-362.5 K, monoclinic, C2/c, a = 17.534(5), b = 9.908(4), c = 30.011 (13) A, β = 108.27(3)°, V = 4951 (3) A 3 , Z = 8, D x = 1.468 Mg m -3 , μ = 1.06 mm -1 , R = 0.021 for 3989 observed reflections [I ≥ 3σ(I)] ; (2), m.p. 447-449 K, triclinic, P1, a = 9.145(6), b = 16.562(5), c = 18.010(8) A, α = 77.72(3), β = 78.52(5), γ = 81.70(4)°, V = 2597(2) A 3 , Z = 4, D x = 1.399 Mg m -3 , μ = 8.24 mm -1 , R = 0.037 for 6993 observed reflections [I ≥ 3σ(I)]. For (1), the molecular structure completely deviates from the usual 4 symmetry found for the para-analogue, but molecules of (2) have distorted 4 symmetries with the methoxy groups having the all-exo conformation. The occurrence of these unsymmetric structures is attributed to the need to maximize crystal lattice stability to offset, in the case of (1), the exigent packing requirements of the meta-CH 3 O groups, and in the case of (2), the intrinsically high molecular energy compared with the tetraphenyl archetype.