The isotypical crystal structures of the mixed valent trihalides PtCl₃ and PtBr₃ were redetermined by single crystal methods (space group R3¯; trigonal setting; PtCl₃: a = 21.213Å, c = 8.600Å, c/a = 0.4054; Z = 36; 1719 hkl; R = 0.035; PtBr₃: a = 22.318Å, c = 9.034Å; c/a = 0.4048; Z = 36; 1606 hkl; R = 0.027). A cubic closest packing of X^— anions forms the basis of an optimized arrangement of cuboctahedrally [Pt₆X₁₂] cluster molecules with Pt^II and enantiomers of helical chains of edge‐condensed [PtX₂X_4/2] octahedra with Pt^IV in cis‐Δ‐ and cis‐Λ‐configuration, respectively. The bond lengths vary with the function of the X^— ligands (d¯(Pt^II—X) = 2.315 and 2.445Å; d¯(Pt^II—Pt^II) = 3.336 and 3.492Å; d(Pt^IV—X) = 2.286 — 2.417Å and 2.437 — 2.563Å). The Pt^II atoms are shifted outwards the X₁₂ cuboctahedra by 0.045Å and 0.024Å, respectively. The symmetry governed Periodic Nodal Surface, PNS, perfectly separates the regions of different valencies. Quantum chemical calculations exclude the possible additional interactions between Pt^II and one of the exo‐ligands of Pt^IV.