ZrO 2 light diffuser layers was placed on phosphor-in-glass composites (PiGs) to improve color uniformity of white-light-emitting diodes (white LEDs). Color coordinates of central part and periphery of white LEDs were (0.34, 0.38) and (0.36, 0.43), respectively; difference between two area decreases with the introduction of a diffuser layer. Color temperature difference also decreased from 770 to 464 K. The addition of diffuser layers reduced the luminous efficacy of the white LEDs from 90.3 to 83.4 lm/W.