Four molecular Pt–carbonyl clusters decorated by Cd–Br fragments, i.e., [Pt₁₃(CO)₁₂{Cd₅(μ-Br)₅Br₂(dmf)₃}₂]²⁻ (1), [Pt₁₉(CO)₁₇{Cd₅(μ-Br)₅Br₃(Me₂CO)₂}{Cd₅(μ-Br)₅Br(Me₂CO)₄}]²⁻ (2), [H₂Pt₂₆(CO)₂₀(CdBr)₁₂]⁸⁻ (3) and [H₄Pt₂₆(CO)₂₀(CdBr)₁₂(PtBr)_x]⁶⁻ (4) (x = 0–2), have been obtained from the reactions between [Pt_3n(CO)_6n]²⁻ (n = 2–6) and CdBr₂·H₂O in dmf at 120 °C. The structures of these molecular clusters with diameters of 1.5–2 nm have been determined by X-ray crystallography. Both 1 and 2 are composed of icosahedral or bis-icosahedral Pt–CO cores decorated on the surface by Cd–Br motifs, whereas 3 and 4 display a cubic close packed Pt₂₆Cd₁₂ metal frame decorated by CO and Br ligands. An oversimplified and unifying approach to interpret the electron count of these surface decorated platinum carbonyl clusters is suggested, and extended to other low-valent organometallic clusters and Au–thiolate nanoclusters.