CdS is a large band gap material compared to HgS. Both are interesting from academic and technological points of view. The nanodispersions (colloids) of CdS and HgS as well their core-shell products and composites (co-colloids) were prepared by varied modes of precursor addition in micellar solution of cationic surfactant cetyltrimethylammonium bromide (CTAB). The prepared dispersions were studied by spectroscopic and electron microscopic techniques.