Variation of the chemical composition of ternary CdS1-xSex nanocrystals grown in borosilicate glass depending on the thermal treatment is studied by resonant Raman spectroscopy. It is shown that only for the nanocrystals with roughly equal content of substitutive S and Se chalcogen atoms (0.4 < x < 0.6) the nanocrystal composition is independent of the thermal treatment parameters. In other cases an increase of the thermal treatment temperature (625-700 degrees C) and duration (2-12 h) results in a considerable increase of the predominant chalcogen content in the nanocrystals. (C) 2010 Elsevier B.V. All rights reserved.