The angular dependence of the elastic scattering of helium atoms from a low coverage (Theta(CO) = 0.03) of randomly distributed isolated CO molecules adsorbed on a Pt(111) surface has been measured over a wide range of incident helium atom beam energies between E-i=5.25 and 62.1 meV. The results are compared with a close-coupling theory for a realistic He-CO potential. From a best fit of the experimental results the distance of the molecule from the surface and a modified gas phase He-CO potential are obtained.