Abstract
A population of young circumstellar disks have different Spectral Energy Distributions (SEDs) with respect to typical disks, showing a deficit of emission in the near-IR and an excess at mid-IR wavelengths. These SEDs have been interpreted as produced by disks with inner holes, which have been classified as ``Transitional Disks''. These disks are considered the evolutionary link between the full disks typically found around the young T Tauri and Herbig Ae stars, and the debris disks, found around some main sequence stars. In this contribution we summarize the observed/inferred characteristics of these transitional disks and also some of the models proposed to explain their peculiar geometry.
