High angular resolution provided by adaptive optics on ground-based telescopes allows detailed study of bright starsenvironment. The limitation of dectability of faint companions isthe diffracted light from the star. The 4Q coronagraph(Rouan et al. 2000; Riaud et al. 2001; Abe et al. 2001) decreases this diffracted haloand provides high contrast imaging. The residual speckle patternbecomes the final limitation for the coronagraphic observations.We present here, a complete study of the 4Q coronagraph in usewith an high order adaptive optics on the VLT telescope, withinthe context of "Planet Finder" ESO project. Practically, a simplesolution making use of commercial half waveplates seems wellsuited for a ground-based coronagraphic device.