(hereafter PSF) analysis removes most artefacts, while all asteroids are eliminated because they move between the two exposures taken at each pointing. Supernovae and other strongly variable objects have to be rejected during the follow-up, but their numbers are kept low thanks to the relative shallowness of the survey. Since we select all PSF-looking $z'$-band dropouts, CFBDSIR also very efficiently identifies high-proper motion objects: if the proper motion is high enough that a $J$-band source cannot be cross-matched with its $z'$-band counterpart, the automatic pipeline keeps the candidate in the selection as a $z'$-band dropout. Visual examination of all selected candidates subsequently identifies those high proper motion sources easily.\
[**NIR Follow-up.**]{} The NIR follow-up of CFBDSIR candidates removes the remaining candidates but also provides an efficient characterisation of the confirmed candidates. Ultracool brown dwarfs can be singled out by their blue $J-H$ and $H-K$ colours owing to stronger H$_2$O, CH$_4$ and probably NH$_3$ absorption than earlier T dwarfs. The CFBDSIR follow-up of the first 66 square degrees from CFBDSIR required about 3.5 nights on SOFI [@Moorwood.1998] at NTT. We were able to observe all 55 T-dwarfs candidates identified and to confirm 6 of them as T-dwarfs, including 3 ultracool brown 