This article covers the literature in the period 2008–18 on five-membered rings with two adjacent heteroatoms with at least one selenium or tellurium (not, however, including 1,2-selenazoles). X-ray crystal analyses on a large selection of compounds revealed strong non-covalent interactions between a ring-selenium atom and an adjacent heteroatom within the molecule (i.e., adjacent heteroatom not part of the heterocyclic ring). Several ring-opening reactions under various conditions (in some cases by the generation of metal complexes) of naphtho[1,8-c]-1,2-diselenole/1,2-thiaselenole and of 1,2-diselenolanes/1,2-selenatellurolanes/1,2-ditellurolanes are covered. The article includes a series of oxides of 1,2-tellurazoles, their assembly into supramolecular aggregates according to X-ray crystallography, their synthesis and reactions. Various synthesis protocols are in general presented, in particular for the preparation of a large selection of 1,2-oxaselenoles, some as spiro compounds and some as cyclic seleninate esters. Many of the compounds described in the article were found to function as glutathione peroxidase mimetics.