The excitation and emission energies of the transition between the lowest 3d¹⁰ singlet and 3d⁹4s triplet states of Cu⁺ ions in ZSM-5 have been studied by a combined quantum mechanics/interatomic potential function technique for different sites of Cu⁺. In the triplet state, the coordination of the Cu⁺ ion to the zeolite framework is significantly different from that in the singlet state. The Cu⁺ ion moves away from the wall of zeolite channels, and it is coordinated only to oxygen atoms of an AlO₄ tetrahedron. Therefore, the emission energies depend not only on the type of the Cu⁺ site but also on the position of the Al atom in the zeolite framework. The smallest emission energies (corresponding to 520−540-nm peaks in observed emission spectra) are found for Al located at the intersection of two channels. The higher-emission energy peaks observed at 470−490 nm are due to the Cu⁺ sites where copper is located inside one of the channels. Because in the triplet state the optimized structures are alike for all Cu⁺ sites considered, the emission energies are also relatively similar. In the singlet state, different types of the Cu⁺ coordination exist, which cause large variations in excitation energies. Our results indicate that photoluminescence excitation scan should be preferably used for Cu⁺ site determination.