Hybrid organic-inorganic materials of the type (diamine)MeSO4 (Me = Cd, Zn) [diamine = p-xylylenediamine (PXDA) or m-xylylenediamine (MXDA)] have not been described in the literature to date. Four compounds of this type, namely, (MXDA)ZnSO4 (1), (MXDA)CdSO4 (2), (PXDA)ZnSO4 (3), and (PXDA)CdSO4 (4), were synthesized by solvothermal methods. Since all compounds crystallized as very fine powders, crystal structure studies were performed using powder diffraction methods. All compounds crystallize in the orthorhombic crystal system and the cell parameters are: a = 9.8004(4) Å, b = 10.7829(3) Å, c = 4.88473(19) Å for 1; 9.8824(10), 11.0907(7), 4.9663(5) Å for 2; 9.8496(3), 21.2419(5), 4.89556(17) Å for 3; and 10.1136(4), 21.6625(3), 4.9562(2) Å for 4. The compounds with MXDA as a linker, crystallize in the space group P21ma, those with PXDA in Pnma. These hybrid materials are built of inorganic monolayers [–Me–(SO4)–] joined by organic linkers created by diamines (PXDA or MXDA). Me metal ions and SO42– anions form layers with a honeycomb structure. In addition to crystal structure, chemical analyses and SEM investigations were performed. Thermal stability of the compounds was also investigated using TG-DSC methods and XRD as a function of temperature.