A simple technique for improving 3-D resolution in confocal scanning microscopy is presented. The technique is based on the equal contribution to the image of the illuminating and the collecting lenses. It is proposed, then, to apodize such lenses with complementary filters, the one designed for increasing the resolution in the image plane, and the other for achieving axial superresolution. Each pupil independently introduces zeros in the point spread function, the positions of which can be chosen to lie in the focal plane or along the optic axis. The combined action of both filters produces a narrowing of the point spread function of the system both in the image plane, and along the optical axis. A numerical example with two well-known pupil filters is carried out.