Abstract. The carbonate Na 4 Cd 3 (CO 3 ) 4 (OH) 2 was synthesized by hydrothermal methods and the crystal structure was established by singlecrystal X-ray diffraction. Na 4 Cd 3 (CO 3 ) 4 (OH) 2 crystallizes in the monoclinic system with space group P2 1 /c (No.14). The structure of Na 4 Cd 3 (CO 3 ) 4 (OH) 2 is built-up from [Cd 3 (CO 3 ) 4 (OH) 2 ] ϱ layers which