- Active Galactic Nuclei (AGN) population in X-ray surveys (e.g., COSMOS, CDFS, X-SERVS, XXL) and their multi-wavelength properties
- The AGN population at high redshifts: from SDSS-like quasars to obscured AGN
- Broad-band spectral energy distributions of AGN: accretion vs. star-formation activity
- Obscured AGN population: X-ray vs. optical vs. mid-IR selection
- Compton-thick AGN, from the local Universe to the very high redshifts
- The AGN content in infrared-selected sources
- Physical properties of local AGN and their close environment
- Dual and multiple AGN systems at low and high-redshift.
- Bolometric output from Type 1 and Type 2 AGN; Eddington ratio and black hole mass estimates
- The dust content in high-redshift quasars
- Broad- and narrow-absorption line quasars (BALQSOs, NALQSOs) as test cases for outflowing winds.