Electron emission properties of Sb- or Sn-doped indium tin oxide (ITO) thin semiconductor films have been studied. These films were deposited using a constant-current ion sputtering method onto the surfaces of a glass slide. On one side a 1-mum-thick film was deposited as a field electrode, and on the other side, 10-200 nm films were deposited as an electron emitter. The films were examined using electric field-induced electron emission. The investigation showed that in the glass-ITO systems field-induced electron emission and photoemission occur, with the yield depending on the field intensity of the emitter, the ITO film thickness and the composition of the film. Electron emission occurs when polarizing voltage is applied and/or the film is UV-illuminated. A phenomenological model of ITO film partition into the two zones, one depleted and the other one enhanced in carriers, is given to explain the effects observed.