FWHM as a function of the total observed [OIII]λ5007 Å luminosity () for different AGN samples. WISSH quasars (red stars) are compared with other samples of Type 1 and Type 2 AGN at low (z< 1, empty symbols) and high (z> 1, filled symbols) redshift. We plot the values obtained for a sample of obscured (Greene et al. 2009; Brusa et al. 2015; Perna et al. 2015a), red (Urrutia et al. 2012), Type 2 (Villar-Martín et al. 2011; Liu et al. 2013), luminous z ~ 2.4 (Cano-Díaz et al. 2012; Carniani et al. 2015), KASHz at z ~ 1.1 − 1.7 (Harrison et al. 2016), and radio quasars (Kim et al. 2013), and those obtained for the local and high-z ULIRGs by Rodríguez Zaurín et al. (2013) and Harrison et al. (2012), respectively. The average values in two bins for optically selected Type 2 AGN in Mullaney et al. (2013) are also shown.