Salvation Army Major Neil Dickson said a lot of preparation had gone into the free lunch, which brought together about 500 Salvos clients at the Brisbane Convention and Exhibition Centre.

"There's been a lot of effort, a lot of teamwork, going in to getting people here and getting them fed," he said.

Major Dickson said the lunch was "a great expression" of how the community could get behind those who were doing it tough.

"The people who are here today are people who have used the Salvation Army services over recent months," he said.

"It could be families that are finding it very tough financially, there are some homeless people here who have been using our shelters, some women and children who have really had a tough time at home and have had to escape a difficult situation.

"So there are a whole range of people enjoying today."

Among those enjoying the chef-prepared meal and the entertainment was Woolloongabba man Kenny Lynn, who was moved by the experience.

"It shows there are still people that care for other people," he said.

One of Mr Lynn's dining companions, Steven Koop of Acacia Ridge, said the lunch was an eye-opener.

"One of the reasons I like to come here is you get to see the cross-section of people that are here and there's so many of us in the same boat," he said.

"It's a reminder, in a very real sense, that you can go anywhere and find people in trouble."

BCEC marketing and communications manager Gail Sawyer said about 50 of the centre's staff, from chefs to car park attendants, had donated their time to host the event.

The BCEC also provided the venue free of charge.

"This is one of the highlight events on our calendar and, after the G20, it's a lovely change," Ms Sawyer said.

"We work with the Salvation Army to put it on but our suppliers help us with some lollies, some food, Village Roadshow generously gives us 500 passes to the theme parks for the kids.

"It's just a real pleasure for us to do it and our staff really look forward to it."

Ms Sawyer said 2014 was the sixth time the BCEC had hosted the Salvos' Christmas lunch.