A study of the crystallographic and magnetic structure of the double perovskite Sr2CoMoO6 (SCMO) has been carried out on a polycrystalline sample using neutron powder diffraction (NPD) data between 10 and 700 K. An analysis of the NPD patterns at room temperature has shown that this compound crystallises in the tetragonal space group I4/m with a = 5.5616(1) angstrom and c = 7.9470(2) angstrom and has a 1:1 ordered arrangement of Co and Mo at the B-sites. This compound undergoes a I4/m -> Fm3m improper ferroelectric phase transition near 560 K. A low-temperature antiferromagnetic ordering (below T-N = 36 K) has been followed from sequential NPD data analysis. The antiferromagnetic structure is defined by the propagation vector k = (1/2, 0, 1/2). In addition to the obtained experimental results on magnetic and electric properties some aspects of magnetoelectricity in this perovskite are also discussed. (c) 2005 Elsevier Ltd. All rights reserved.