Contrast limit for the direct imaging of extrasolar planets from ground based adaptive optics (AO) observations is set by the presence of static and slow-varying aberrations in the optical path that lead to the science instrument. To complement the otherwise highly successful angular differential imaging (ADI) technique toward small angular separation, we propose to employ additional wavefront control to modulate the diffraction. This flexible approach introduces enough diversity to discriminate genuine structures of the observed target from spurious diffraction features in the image. One possible implementation of such form of coherence differential imaging (CDI) is a speckle nulling algorithm that iteratively suppresses diffraction features inside a region constrained by the number of active elements of the deformable mirror modulating the wavefront, and the coronagraph. This paper presents on-sky results obtained with this approach, on the Subaru Coronagraphic Extreme AO (SCExAO) instrument.