Being intrinsically faint objects, the detection of ultracool dwarfs is not straightforward. In fact, very few of them were known until the advent of global surveys at deep optical and near-infrared wavebands like 2MASS, SDSS, DENIS or, more recently, UKIDSS.
The identification of ultracool objects usually requires mining the sky through an appropriate combination of attributes available from different archives (e.g. colours and/or proper motion information), a tedious and time-consuming task if a “classical” methodology is used. Conversely, the navigation across large databases in an efficient and organized way is an approach that perfectly fits the framework of the Virtual Observatory.