High-resolution Compton scattering spectra of methane, methane hydrate, and ice were measured using incident photon energy of 56.4 keV at beamline ID15B of the European Synchrotron Radiation Facility. The experimental Compton profiles are compared to calculations employing density-functional theory using model atomic clusters. The hydrate has a cagelike structure built up from water molecules and the related Compton profile is observed to change apparently when compared to hexagonal ice. Furthermore, the influence of the guest-host interactions between the methane molecules and the water molecules of the cages on the Compton profile is discussed. ; system details: machine converted author identifier PE to PID, February 2012