H&M account manager Amy O'Shaughnessy said clothes created exclusively for the Australian market were among the best sellers over the weekend.

The "AU Leather Jacket" and the "AU Exclusive Jumper" were the biggest hit with Aussie shoppers, while other favourite items included the "Ladies Trend Skirt" and "Ladies Trend Tunic".

On Monday, a spokeswoman for H&M told Fairfax Media that the new department store situated in Melbourne's historic GPO building attracted more than 15,000 customers on Saturday, its first day of trade.

She confirmed it was one of the best country launches in the retailer's history. The Swedish fashion and homewares group operates in more than 50 countries.

And it appeared the excitement had yet to abate on Monday afternoon, as thousands of eager shoppers waited for hours outside the massive store.

Burly security guards, armed with two-way radios and decked out in steel-grey suits controlled the huge line of customers, which stretched back for more than a block.

Filled mostly with chattering and excited teenagers, it seemed that opening the popular global department store just before the start of school holidays was a fortunate coincidence.

School friends Emma, Sam, Nina, Cindy and Lian were among those who could not wait to get inside.

Emma, 15, said she had loved shopping at the store overseas and wanted to see what the first H&M would look like in Australia.

But for Sam, also 15, it was the cheap clothes that did it.

“They just have really good prices and really good clothes,” he said excitedly.

For others, an outing to H&M with friends was an experience in itself, and a much better alternative to online shopping.

“You always hear that fashion overseas is better than in Australia, and even though you can go online, it's just not the same experience as going with your friends and trying clothes on,” Cindy, 16, said.

Grandmother Rosa Presta, her daughter Pina and granddaughter Jessica set out for a family day of shopping, not expecting Australia's flagship store to be so “amazing”.

Like many other fashionistas, all three had seen H&M overseas, but they were nonetheless impressed by the down-under version.

“It's just all so coordinated,” mum Pina said.

“All the skirts are together, all the shirts, belts and so on. It makes shopping so much easier.”

Grandmother Rosa was also inspired by the complete outfits featured on most mannequins around the shop.

“You can just come in and buy an entire outfit,” she said.

The store, which fills the entire GPO building, is light, airy and spread out, with all racks accessible and a maximum capacity of 1000 allowed, giving shoppers ample room to roam.

“I love that the store is so bright and big – it's actually much nicer than those overseas,” Jessica said.