Hα criteria (blue lines) to select CTTS and WTTS (White & Basri 2003). (a) Hα equivalent width vs. spectral type. (b) Hα equivalent width vs. Hα width at 10% of maximum intensity. Transition disk candidates are predominantly found among accreting systems. Therefore, the presence of a hole in the inner disk does not stop the accretion process, suggesting that gas is flowing through the hole. Systems for which we do not have data at 22/24 μm are identified by gray filled symbols.