But from Tuesday, more than 15,000 of the ACT's youngest patients a year will have access to this family-friendly waiting, triage and treatment area away from the chaos of the general hospital.

Based on the best designs from around Australia and the world, the $5 million department includes six beds, two consultation rooms and a private waiting area.

It also includes a change room, an isolation room and more private treatment spaces.

Canberra Hospital deputy director-general Dr Ian Thompson said the unit provides a safe haven for children and their families while they are being treated.

"It provides an environment that's welcoming for children and will hopefully reduce their anxiety in what can be a very worrying time," Dr Thompson said.

"We've got a dedicated waiting area which means children can come straight through here and not have to wait in the main waiting area, so they don't have to see other patients who are presenting and some of the sick adults who are here."

While the unit won't have dedicated paediatric emergency staff, Dr Thompson said all of the department's staff are trained to care for children.

"On each shift we will roster people specifically to this area and we will always have staff available to care for the children," Dr Thompson said.

ACT health minister Simon Corbell said one in five patients treated in the emergency department were aged under 15 years, which is why a dedicated paediatric treatment space was warranted.

"We know coming to an emergency department can be a very difficult and a very traumatic time," Mr Corbell said.

"As a parent or as a young person being confronted with the difficult things happening inside an ED, and the fact you are seeing other people who are sick and dealing with their own health problems, can make it a very trying experience."

The opening of the department marks the completion of the second stage of the $23 million emergency department expansion at the Canberra Hospital.

Once completed, the ED's capacity will increase by a third to 75 treatment spaces.

But while both the ACT's health and assistant health ministers attended the launch, Canberra Hospital staff said they did not merit an invite.

Some staff contacted Fairfax Media to express their disappointment at the politicisation of the event.

Australian Nursing Federation ACT Branch president Jenny Miragaya said the union was not invited to the launch and "didn't even know it was on".

Canberra Hospital's emergency department has previously been slammed as one of the most inefficient and expensive in the nation.

Mr Corbell said the modernised paediatric department was a "very important complement to the overall rebuild" of the emergency department.