The invention aims at thoroughly slimming down video cameras or digital cameras using a zoom system that is composed of a reduced number of lens elements, diminished in size and simplified in construction, and has high image-formation capability. A zoom lens for use on an electronic imaging system comprises a negative first lens group G1, an aperture stop S, a positive second lens group G2 and a positive third lens group G3. Upon zooming from the wide-angle end to the telephoto end of the zoom lens, the second lens group moves only toward the object side of the zoom lens and the third lens group moves in a locus different from that of the second lens group. The first lens group is composed of a negative lens element having an aspheric surface and a positive lens element. The second lens group comprises an object side-lens component and an image side-lens component. One of the lens components comprises a doublet component consisting of a positive lens element and a negative lens element, and the other consists of a positive single lens element. The object side-surface of the object side-lens component is defined by an aspheric surface. The third lens group comprises one lens component having positive refracting power. The object side-lens component in the second lens group satisfies condition (1) concerning the radius-of-curvature ratio between the object side-surface and the image side-surface.