Schematic illustration of an AGN being both a quasar (luminous thermal emission from the accretion disc) and a blazar (even more luminous non-thermal emission from the relativistic jet), i.e. an FSRQ like 3C 454.3. It is assumed here that the BLR is concentrated along the accretion disc plane at characteristic distance R_BLR from the SMBH. The optical continuum is dominated by the synchrotron radiation produced in a blazar zone located within the jet at characteristic distance r_blazar, and the Mg II BEL is produced in the BLR.