Since the discovery in 1995 of the first extrasolar planet candidate around a solar type star using the radial velocity method, to date (beginning of 2005), 135 candidate planets around main sequence stars have been discovered by the transit and the radial velocity (RV) methods. Their minimum masses are in the range 0.045 to 13 MJup. The proximity of these planets to their host stars has prevented direct imaging and spectroscopy, making a precise characterisation of their physical structure and chemical composition difficult.The aim of the JOVIAN project (Jupiter-like Objects in the Visible and in the Infrared: their Astrophysical Nature; P. I.: R. Rebolo) is to achieve the direct detection and characterisation of objects down to the mass of Jupiter, and help, through selected observations, to shed light on the formation of massive planets.