The structure of CsLuW/sub 2/O/sub 9/ was determined from single-crystal X-ray diffraction data with a = 9.322(3), b = 5.132(6), c = 7.277(4) A, and ..beta.. = 95.66(4)/sup 0/, in the space group P2/c. It is composed of double chains of distorted WO/sub 6/ octahedra that share an edge across the chain and share opposite corners along the chain in the c direction. The tungsten-oxygen chains are interconnected via the lutetium and cesium atoms which are in eight- and twelve-coordination with oxygen. A comparison with the related structure of KYW/sub 2/O/sub 8/ is made. The compounds CsLnW/sub 2/O/sub 8/ (Ln = Y, Gd) have a similar structure. The three tungstates (Ln = Y, Gd, Lu) exhibit an intense luminescence at room temperature, whereas KYW/sub 2/O/sub 9/ does not luminesce at all. The luminescence of the compounds with Ln = Eu, Tb are also reported.