The results of the study of the luminescent properties of the CdS(Se) quantum dots (QDs) with the mean size of 2-4 nm synthesized in the fluorine phosphate glass are discussed. The changes of the photoluminescence absolute quantum yield (PL AQY) magnitude of the CdS(Se) QDs with various mean sizes induced by the heat treatment are studied. It was found that the PL AQY of the CdSe QDs increases monotonically to a maximum and then fells down. PL AQY magnitudes for glasses doped with CdS QDs demonstrate weak dependence on the size. It was found that CdS(Se) QDs represents a series of excellent emitters in the 600-750 nm spectral region. PL AQY in the glasses can reach 50-65%, which is equal to the value in the colloidal nanocrystals and higher than it was reported earlier for the silicate glasses. The glass matrix protects the QDs from external influence and their optical properties remain unchanged for a long time.