A light emitting device, a light emitting device package, and a lighting system are provided. The light emitting device includes: a second conductive semiconductor layer; an active layer over the second conductive semiconductor layer; a first conductive semiconductor layer over the active layer; and a second electrode layer including a reflective layer under the second conductive semiconductor layer. The active layer includes a second active layer that actually emits light on the reflective layer and a first active layer that does not emit light on the second active layer. A distance between the reflective layer and the second active layer satisfies a constructive interference condition.