Polarimetry is a powerful tool for detecting and characterizing exoplanets and protoplanetary disks as light scattered from circumstellar material is linearly polarized. We present the first light results of ExPo (Extreme Polarimeter) , a sensitive imaging polarimeter developed at Utrecht University that works in the visible part of the spectrum. Our first light observations at the 4.2-meter William Herschel Telescope (WHT) show that ExPo can reach the high-contrast ratios that are necessary to observe protoplanetary disks. We present images of the protoplanetary disks around the Herbig Ae star AB Aurigae and the T Tauri star SU Aurigae. Our results show the power of polarimetry for future projects e.g. the ZIMPOL arm of SPHERE, and the EPOL part of EPICS.