The volunteer-run, not-for-profit Brick Expo opened on Friday at the Hellenic Club at Woden and continues on Saturday and Sunday.

It hopes to raise $60,000 for major charity PaTCH to purchase much needed medical equipment for Paediatrics at the Canberra Hospital.

Brick Expo chair David Boddy said 12,500 people visited the event last year. They hoped to sell 9000 tickets for this show, its seventh, but sales were as low as 4000 last week.

Mr Boddy believed sales had been affected by the Towers of Tomorrow with LEGO® Bricks exhibition now on at the National Museum of Australia, with the public confusing the two.

"We really noticed the impact it had," Mr Boddy said.

"We were wondering if we'd even be back next year ticket sales were that bad.

"We spend a lot of money on television advertisements, it's what we need to do to promote the event, and unfortunately it meant selling a lot of tickets for another show that's on.

"It's a little disappointing because we do a lot of things with the National Museum so to not be included was unfortunate."

Brick Expo organisers upped their campaign on social media, getting enough ticket sales to ensure the event return will return next year.

"We're basically past that threshold now so every ticket sold now is going straight into the hospital," Mr Boddy said.

"There is no profit for us, we're purely not-for-profit. It's a community event."

Mr Boddy said he hoped a similar situation didn't arise in the future.

"I don't think Canberra can support two shows on at the same time," he said.

A National Museum of Australia spokeswoman said the timing of the Towers of Tomorrow exhibition was determined by its" availability with only a small window of opportunity to bring this wonderful show to Canberra audiences before it heads to the United States".

She said the museum was "big supporters of our friends at Brick Expo Canberra".

"Visitors to the Towers of Tomorrow exhibition are being handed pamphlets promoting this year's Brick Expo and we hope the cross promotion benefits this important initiative - and that Canberrans are inspired to seek out even more Lego building opportunities as a result," she said.

Visitors to Brick Expo on Friday including plenty of wide-eyed children were simply enchanted by the Lego creations across three rooms at the Hellenic Club.

Oscar Williams, 11, of Florey, loved the Minecraft Lego displays.

"It's awesome," he said.

"Look at the size of this creeper! Please don't explode!"

Monash public servant Russell Murphy spent six months building a 4000-piece moving ferris wheel from Lego.

"You can grow up without growing up," he said, of his love of Lego.

Isabella Plains banker Jacob Krog is from Denmark, the land of Lego, and his love of the bricks is in his blood. He has created a wondrous Disney on Ice Lego piece.

"I got my first Lego when I was six years old and when my two boys were old enough, my mother gave them Lego," he said.

Mr Boddy, a 3D animator for an engineering company, encouraged as many people as possible to come and see the fantastic Leo creations made by the volunteers who come from around New Zealand and Australia, from Star Wars to Big Ben; Bananas in Pyjamas to Where's Wally?

"Lego is a great tactile release. It's my therapy and it gets me away from the computer," he said.

"Lego modellers - they're all show offs! They want to show off their stuff."

Brick Expo is at the Hellenic Club in Woden on Friday , August 11 until 6pm; Saturday, August 12, from 9am to 6pm and Sunday, August from 9am to 4.30pm.

Tickets are still available at brickexpo.com.au.