The cerium-doped oxyorthosilicates Lu2SiO5 (LSO), Y2SiO5 (YSO), and Gd2SiO5 (GSO) are well-known single-crystal scintillators with well-characterized properties, which are commonly used for gamma-ray detection. LSO and YSO share the monoclinic C2/c structure in which the two rare earth sites, which are also the cerium substitutional sites, have coordination numbers 6 and 7. GSO differs in that it has a monoclinic P2(1)/c structure, in which the two rare earth sites have coordination numbers 7 and 9. Prior work has shown that cerium doped LSO and YSO can be very successfully codoped with Ca2+, increasing the light yield and shortening the decay time in a reproducible, predictable way. It is known that this aliovalent codoping results in a significant reduction in shallow charge carrier traps in both YSO and LSO without any significant changes in the emission and excitation spectra. This current work extends that prior investigation; in this case, the scintillation properties of cerium doped GSO single crystals, with and without Ca2+ codoping, are compared with those of LSO and YSO single crystals. (c) 2012 Elsevier B.V. All rights reserved.