In order to investigate the effect of microstructure on the brightness of thin film phosphors for field emission displays, Y2O3:Eu thin film phosphors were prepared using pulsed laser deposition. To deconvolute the effects experimentally, the Y2O3:Eu films of controlled thickness and microstructure were prepared on various substrate materials such as amorphous quartz, (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon wafers. Cathodoluminescent brightness and efficiency of the films were obtained in both transmission and reflection modes. The Y2O3:Eu films deposited on the quartz substrates showed the maximum brightness followed by the films on (0001) sapphire, (100) lanthanum aluminate (LaAlO3), and (100) silicon substrates. The role of interface scattering of the emitted light on the film brightness will be discussed together with changing surface roughness and film thickness.