Na2Cd2O3 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form distorted NaO4 trigonal pyramids that share corners with six equivalent Na(1)O4 trigonal pyramids, corners with six equivalent Cd(1)O4 trigonal pyramids,  an edgeedge with one Na(1)O4 trigonal pyramid, and edges with two equivalent Cd(1)O4 trigonal pyramids. Cd(1) is bonded to one O(1) and three equivalent O(2) atoms to form distorted CdO4 trigonal pyramids that share corners with five equivalent Cd(1)O4 trigonal pyramids, corners with six equivalent Na(1)O4 trigonal pyramids,  an edgeedge with one Cd(1)O4 trigonal pyramid, and edges with two equivalent Na(1)O4 trigonal pyramids. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Na(1) and two equivalent Cd(1) atoms to form corner-sharing ONa4Cd2 octahedra. The corner-sharing octahedral tilt angles are 45°. In the second O site, O(2) is bonded in a 5-coordinate geometry to two equivalent Na(1) and three equivalent Cd(1) atoms.
Na2Cd2O3 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form distorted NaO4 trigonal pyramids that share corners with six equivalent Na(1)O4 trigonal pyramids, corners with six equivalent Cd(1)O4 trigonal pyramids,  an edgeedge with one Na(1)O4 trigonal pyramid, and edges with two equivalent Cd(1)O4 trigonal pyramids. There is one shorter (2.32 Å) and one longer (2.34 Å) Na(1)-O(1) bond length. There is one shorter (2.29 Å) and one longer (2.50 Å) Na(1)-O(2) bond length. Cd(1) is bonded to one O(1) and three equivalent O(2) atoms to form distorted CdO4 trigonal pyramids that share corners with five equivalent Cd(1)O4 trigonal pyramids, corners with six equivalent Na(1)O4 trigonal pyramids,  an edgeedge with one Cd(1)O4 trigonal pyramid, and edges with two equivalent Na(1)O4 trigonal pyramids. The Cd(1)-O(1) bond length is 2.19 Å. There are a spread of Cd(1)-O(2) bond distances ranging from 2.19-2.31 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Na(1) and two equivalent Cd(1) atoms to form corner-sharing ONa4Cd2 octahedra. The corner-sharing octahedral tilt angles are 45°. In the second O site, O(2) is bonded in a 5-coordinate geometry to two equivalent Na(1) and three equivalent Cd(1) atoms.