Inelastic X-ray scattering spectra of liquid water and cyclohexane have been measured with 2 eV resolution for a momentum transfer range between 0.69 and 2.77 au at BL16A of the Photon Factory, KEK, Tsukuba. Observed spectra are transformed to the dynamic structure factor which is normalized by using the Bethe sum rule, and the static structure factor is obtained. From a comparison with extended CI calculations by the use of various basis sets, correlation effects are proved to be of vital importance in inelastic X-ray scattering.