Context : The young active star BD +20 1790 is believed to host a substellar companion , revealed by radial-velocity measurements that detected the reflex motion induced on the parent star . Aims : A complete characterisation of the radial-velocity signal is necessary in order to assess its nature . Methods : We used CORALIE spectrograph to obtain precise ( \sim 10 m/s ) velocity measurements on this active star , while characterizing the bisector span variations . Particular attention was given to correctly sample both the proposed planetary orbital period , of 7.8 days , and the stellar rotation period , of 2.4 days . Results : A smaller radial-velocity signal ( with peak-to-peak variations < 500 m/s ) than had been reported previously was detected , with different amplitude on two different campaigns . A periodicity similar to the rotational period is found on the data , as well as a clear correlation between radial-velocities and bisector span . This evidence points towards a stellar origin of the radial-velocity variations of the star instead of a baricentric movement of the star , and repudiates the reported detection of a hot-Jupiter . Conclusions :