Silicate glasses were synthesized with additional CdO and ZnSe of varying content. When CdO was added up to 3mol% with the amount of ZnSe fixed at 1mol%, absorption due to Se-2(-) color centers significantly decreased and the color of glasses was bleached without any evidence of CdSe quantum dots (QDs). However, characteristic absorption due to CdSe QDs appeared without additional heat treatment when the ZnSe content exceeded 1.5mol%, whereas the CdO content was fixed at 1mol%. Raman spectra and transmission electron microscopy verified the formation of CdSe QDs. The role of CdO and ZnSe in CdSe QD formation has been discussed in relation to their structural contribution within silicate glasses.