The reactions of HgCl2 with 2,1,3-benzoselenadiazole (bsd) in methanol afforded the polymeric complexes [HgCl2(bsd)2]n (1) and [HgCl2bsd]n (2) in good yields. The crystal structures of 1 and 2 have been determined by single-crystal X-ray crystallography. Complex 1 is an one-dimensional (1D) polymer and consists of (HgCl2)n chains running parallel to the c-axes. Complex 2 is a two-dimensional (2D) polymer and consists of (HgCl2)n chains running parallel to the a-axes and being further bridged by bsd molecules to create a layer lying parallel to the ab plane. Both crystal structures are dominated by π···π interactions between the bsd molecules, while the presence of N···Se interactions increases the dimensionality in 1. Characteristic IR data are discussed in terms of the nature of bonding in the structures of the two complexes.