ABSTRACT This paper discusses the properties of the European Large Area ISO Survey (ELAIS) 15‐μm 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 selection of candidates and for the estimation of photometric redshifts. Colour–colour plots and template fitting are used for these purposes. The properties of the 15‐μm quasar sample, including variability and black hole masses, are studied 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.