Crystal structure of double nitrites MCd(NO2)(3) [M = K, Rb, Cs, T1] at room temperature was ab initio determined from X-ray powder diffraction data. The compounds are isostructural and can be described as rhombohedrally distorted perovskites: space group R3 (no. 146); Z 1; M = K: a = 7.5887(1), c = 9.1285(2) Angstrom; M = Rb: a = 7.6290(1), c = 9.2355(2) Angstrom; M = Cs: a = 7.7305(1), c = 9,4170(3) Angstrom; M = T1: a = 7.6219(1), c = 9.2300(2) Angstrom. The coordination polyhedra of cadmium and M cations are the distorted tricapped trigonal prism [(3O + 3N) + 3O] and cuboctahedron, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.