The chemistry of 1-hydroxybenzotriazole (btaOH) with the group 12 metal ions Zn(II) and Cd(II) resulted in the 1D coordination polymer [Zn(btaO)2]n (1) and the mononuclear complex [Cd(btaO)2(H2O)4]·3H2O (2·3H2O), respectively. Polymer 1 forms double-stranded chains which are further supported by weak C–H⋯O hydrogen bonds resulting in a pcu (primitive cubic) rod packing. The mononuclear complexes of 2 form undulating hydrogen bonded layers while the lattice water molecules form 1D hydrogen bonded tapes, comprising 4- and 6-membered rings, within the layers and bridge them to the third dimension. The thermal and optical properties of both compounds are presented. IR data are discussed in terms of the chemical composition of the compounds and the coordination mode of btaO−.