  This paper discusses properties of the European Large Area ISO Survey 15
micron quasars and tries to establish a robust method of quasar selection for
future use within the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE)
framework. The importance of good quality ground-based optical data is
stressed, both for the candidates selection and for the photometric redshifts
estimates. Colour-colour plots and template fitting are used for these
purposes. The properties of the 15 micron quasars sample are studied, including
variability and black hole masses and compared to the properties of other
quasars that lie within the same fields but have no mid-infrared counterparts.
The two subsamples do not present substantial differences and are believed to
come from the same parent population.
