The asymptotic group of symmetries at null infinity of flat spacetimes in three and four dimensions is the infinite dimensional Bondi-Metzner_Sachs (BMS)group. We show that BMS group is isomorphic to a non-relativistic limit of conformal group. It will be argued that this non-relativistic limit of CFT is equivalent to the flat space limit of AdS spacetimes. We will talk about various subjects which show that this correspondence may make sense.