The far-infrared spectra of platinum(IV) complexes of the types cis- and trans-[PtX4L2](X = Cl, Br, or I; L = donor ligand) are assigned and discussed. For the trans complexes the halogen-sensitive modes occur near those of the related [PtX4]2– species whilst the ν(Pt–X) pattern for the cis complexes covers a wide range which includes that of ν(Pt–X) in bridging situations in platinum(II) compounds. Assignments are given for ν(Pt–P), ν(Pt–As), ν(Pt–S), and for the associated bending modes.