An imaging lens system comprises, in order from an object side to an image side: a first lens element with positive refractive power having a convex object-side surface; a second lens element with refractive power; a third lens element with refractive power having object-side and image-side surfaces being aspheric, at least one surface thereof having at least one inflection point; a fourth lens element with refractive power having a concave object-side surface and a convex image-side surface; a fifth lens element with refractive power having an aspheric object-side surface and an aspheric concave image-side surface, the image-side surface thereof having at least one inflection point.