An inquest will determine whether the deaths of Lindt cafe gunman Man Haron Monis and two hostages could have been prevented.

Barrister Katrina Dawson and cafe manager Tori Johnson died along with Monis in the 16-hour siege as police stormed Sydney's Martin Place cafe last month.

The coronial inquest, beginning in Sydney on Thursday, will seek to determine how the deaths happened.

No witnesses will be called on the opening day, but counsel assisting will outline the scope of the inquest and the results of inquiries made to date.

Lawyers representing police officers, the victims' families, and other interested parties have been invited to apply to take part.

A large international media contingent, including the BBC, CNN and the New York Times, is expected to attend.