Example embodiments relate to a display device having first and second substrates arranged opposite to each other, a semiconductor device on the first substrate, an organic light emitting element on the first substrate and an optical unit between the organic light emitting element and the second substrate. The display device may be configured to adjust angle viewing modes, e.g., a narrow angle viewing mode and a wide angle viewing mode, by selectively applying a voltage to the organic light emitting element and the optical unit.