The decay behavior of Li2SrSiO4:Eu2+, Li2CaSiO4:Eu2+, and Li2BaSiO4:Eu2+ phosphors, which exhibit similar stoichiometries but different structures, differed significantly, even at the same activator concentration. Such differences in decay behavior cannot be elucidated by the traditional energy-transfer model based on homogeneous distribution of activators in the host. In this regard, we examined the decay curves of Li2SrSiO4:Eu2+, Li2CaSiO4:Eu2+, and Li2BaSiO4:Eu2+ phosphors based on the angular class model. It was found that the decay behavior was closely related to the local structure around the activator, indicating that the higher the site symmetry the more active the concentration quenching.