A novel one-step method of preparing Y2O2Se from Y2O3 and Se in a CsCl flux is reported. Pure Y2O2Se and Y2O2Se:1%RE3+ solid solutions were quantitatively prepared and studied. The Y2O2Se sample is stable in air up to 680°C and has a melting point of 2015ºC in an inert atmosphere. Optical properties of Y2O2Se:1% RE3+ samples (RE=Ce – Nd, Sm, Eu, Tb – Yb) were investigated. It was found that Y2O2Se:1%RE (RE=Pr, Nd, Sm, Eu, Tb – Yb) are luminescent at room temperature with characteristic emissions of corresponding ions. Ce3+ or Eu3+ solid solutions are luminescent at 77K and demonstrate quenching at room temperature. The d-f transitions of Ce3+ ions in the Y2O2Se matrix are slightly shifted to lower energies relative to those in the Y2O2S matrix due to the influence of Se2– in the ligand environment of cerium.