CdSe nanocrystals (NCs) embedded in polystyrene (PS) and poly(methylmethacrylate) (PMMA) show a variety of responses when irradiated with light of moderate intensity and above the band gap. In the presence of molecular oxygen, photocorrosion occurs, resulting in an initial photobrightening followed by photodarkening. In PS, NCs show evidence of a rapid quenching mechanism that is believed to be due to NC charging. By far the largest photoinduced effect is a three- to four-fold photobrightening phenomenon that is observed in PMMA. This dominant effect is independent of the ambient atmosphere and is assigned to the adsorption of ester groups to the NC surfaces during irradiation.