3D processing and imaging of diffraction is a challenge in seismic data processing and needs to be focused more. Seismic diffractions carry a lot of information about the subsurface especially in regions with small scale structures e.g. fractures, pinch-outs, thin lenses etc. Thus, diffraction separation and imaging can lead to higher resolution, which is of particular interest for reservoir characterization and exploration. If diffraction-only data are available, they permit to extract information in addition to that obtained from reflection processing. In this work, we suggest a 3D workflow based on common-reflection-surface (CRS) method for prestack diffraction separation and enhancement. Application to a 3D synthetic data set demonstrates advantages compare to poststack diffraction separation. In contrast to poststack diffraction separation, prestack separation workflow makes use of partial CRS which comprises not only the diffraction separation facility but also includes a prestack data enhancement, i.e., an improved SNR in diffraction-only data. It also demonstrates potential for time migration velocity analysis using diffraction-only data.