Mixed CH4/CF4 clusters as well as pure clusters of CF4 were produced by adiabatic expansion and studied by carbon is (C is) X-ray photoelectron spectroscopy. Evidence is presented that CH4 and CF4 do indeed form binary clusters in CH4/CF4 coexpansion experiments and that these clusters exhibit radial structure; i.e., CF4 is primarily found in the bulk. The interpretation of the photoelectron spectra is supported by calculations of Cls ionization energies based on theoretical clusters models.