At least one exemplary embodiment is directed to a zoom lens system, which can have a diffractive optical element, achieves high optical performance over a wide zoom range. The zoom lens system includes a first lens unit having positive optical power, a second lens unit having negative optical power, and a rear lens component including at least one lens unit having positive optical power. The first lens unit, the second lens unit, and the rear lens component are arranged in that order from an object side towards an image side of the zoom lens system. The diffractive optical element is included in the first lens unit. The rear lens component is provided with a positive lens element having extraordinary dispersion characteristics.