LYSO:Ce and LuYAP:Ce are single crystal non-hygroscopic scintillators of high density, high light yield and short decay time, which have been successfully used in small animal PET imagers. In the present study, the luminescence emission properties of (Lu-0.9,Y-0.1)(2)SiO5:Ce (LYSO:Ce) and (Lu-0.7,Y-0.3)AlO3:Ce (LuYAP:Ce) crystals were investigated for use in x-ray medical imaging. Both crystals had dimensions of 2 x 2 x 8 mm(3), with all surfaces polished. Evaluation was performed by determining the x-ray luminescence efficiency (XLE) (emitted light energy flux over incident x-ray energy flux) and the detector optical gain (DOG) (emitted light photons per incident x-ray photon) in a wide range of x-ray energies employed in mammography (22-49 kVp) and in general x-ray imaging (50-140 kVp). Measurements were performed using an experimental set-up based on a photomultiplier coupled to an integration sphere. The emission spectrum under x-ray excitation was measured using an optical grating monochromator to determine the spectral compatibility to various optical photon detectors incorporated in medical imaging detectors. Optical characteristics such as transmission and absorption spectra were investigated in addition to the scintillation properties. The light emission performance of the two scintillation materials studied was found adequately high for x-ray imaging.