The Boxing Day sales are famous — so famous in fact that hundreds of shoppers have lined up overnight at some stores only to find no discounts on offer.

Bleary-eyed and clutching coffees, the people queueing outside one upmarket fashion store on Sydney's Pitt Street began arriving before dawn and formed a line stretching 200m.

But when the doors finally opened at 8:00am, the eager shoppers rushed in only to find there were no discounts.

Not that it seems to have driven the crowds away, as people kept lining up just for the tradition of it.

Over at the major department stores, where discounts of up to 50 per cent were being offered, the first eager shoppers started arriving at 9:00pm on Christmas Day.

It's all part of the fun, they said:

"I got here at 3.45am, which is a bit late actually. It's our Boxing Day tradition, so we've been coming for the last five years. So I'm really excited to get some sales."

"I got here at 4 o'clock, this is my first time here, it's good. This is like a bucket list, tick the bucket list and do it."

"I have a list, actually, I've been working on it for a few months: a suit, leather jacket, blazer, some shoes, some jeans, some casual wear."

"I'm a little bit tired, a bit sleepy. I've got work … but I reckon I can make it. It's the physical thrill."

Retailers are expected to bring in about $2.3 billion in the Boxing Day sales period, and close to $18 billion in the three weeks after.

Sorry, this video has expired Boxing Day sales shoppers share why they love the rush

It's a boom for bricks-and-mortar outlets who have to compete against online shopping, especially since the arrival of Amazon in Australia this month.

But many shoppers flocking to the sales say they still prefer the retail experience.

"I like seeing it in retail and trying things on as opposed to online, and I think it's better for retail."

"I like the energy of the crowds, it's actually lots of fun. People are great to be around in the morning, they're always very happy and friendly."

"If you don't come in today you'll miss out. You'll miss out on size, the colour, so you've got to be in today."

Australian Retailers Association executive director Russell Zimmerman said the crowds were building in Sydney and Melbourne, in particular.

"We're expecting some line-ups at some of the stores in the near future, so things are looking pretty positive at the moment," he said.

"I'm going to say to people, 'Be prepared to wait — retailers can only put so much staff on'.

"You might have to line up to pay or line up to get service. Be prepared to do it and be nice to other people, because everybody wants to enjoy it."