Sr3Ir2O7 has been claimed to realize a novel ground state (the spin-orbit Mott-insulator), first theoretically suggested to be relevant from theories addressing the tuning on of strong spin orbit interaction generally negligible in the well known Mott- 3d transition metal oxides, in the less known 5d TOM¿s. Besides this interest, Sr3Ir2O7 are materials that can interestingly crystallize as Ruddelsen-Popper phases An+1IrnO3n+1 (n=1,2), like High-Tc cuprates. We think it is important to collect high resolution Neutron Powder diffraction data on Sr2Ir2O7, in order to check the original structural model inferred so far only by single crystal X-ray.