Single crystals of two new quaternary bismuth oxychlorides, Bi18O22Cl8.5(BO3)0.5(1) and Bi18O22Cl8Se (2), have been serendipitously produced in syntheses starting from bismuth borate or oxyselenide and oxychloride. The crystal structure of 1 represents a high symmetry analog of the PbBi17O22Cl9 type structure, formed by double aliovalent (Pb2+ → Bi3+, 0.5Cl– → 0.5BO33–) substitution at the two respective cationic and anionic sites, while 2 is a full structural analog of PbBi17O22Cl9. Overall, their structures can be described as sequences of thick (16 Å) slabs (2D “host” structure) comprised of litharge–like layers and ribbons formed by edge-shared oxocentered OBin, polyhedra (n = 4 and 5). The chloride anions fill the 7.6 Å channels with the triangular cross-section inside the slabs as well as the interlayer space wherein they are partially substituted by disordered BO33– groups or Se2– anions. Compound 1 is just the second example of a mixed halide–borate occupancy among bismuth compounds while 2 illustrates much broader perspectives of mixed oxyhalide–oxychalcogenide approach to construction of novel complex bismuth compounds. Both compounds make new contributions to the family of tunnel structures of anion-centered tetrahedra featuring wide trigonal channels filled by halide anions or more complex metal–halide “salt inclusions”.