The portrait of a heavy-set, rather austere-looking gent called Honus Wagner sold a few weeks ago to an anonymous collector for £1.3m. Journalists were summoned to a press conference in Los Angeles where the picture was displayed under armed guard.

There is nothing exceptional about that, you might think, in these days when paintings sometimes sell for tens of millions. But the Wagner picture was not a painting. It was a mass-produced card, given away free with packets of cigarettes.

The card dates from 1909 and was reputedly withdrawn because Wagner, a baseball player with the Pittsburgh Pirates, did not want to encourage smoking. The withdrawal created a shortage, though there are at least another 25 such cards known to exist and the sale reflects a boom in prices for old collector cards.

"The things that have gone up a lot in the last 10 years have been the early cigarette cards, pre-1918, and I think the biggest rise of all is the 1960s-1970s bubblegum cards," said Ian Laker, managing director of the London Cigarette Card Company, which is 80 this year.

Just about every boy who grew up in the 1960s will have vivid memories of gory American Civil War bubblegum cards.

Everyone had their own little stash, bound with a rubber band, swapped at play time - "Got, got, got, not got" - till the set of 88 was complete. They were then shoved away in some drawer and probably disappeared somewhere down the line. These days, sets routinely fetch £100 on eBay.

There were cards featuring the Beatles, Thunderbirds, The Man from UNCLE and the Second World War, each one little more than three inches by two. Footballers were a hardy annual. The gum card market is one of the few places where Scottish league footballers are routinely worth more than their English counterparts - because Scottish cards are rarer.

It's a boy thing, people say, this urge to collect. But girls - and women - collect too. The female passion for Beanie Babies fuelled a boom in modern collectibles in the 1990s.

Actress Diane Keaton collects clown paintings and has been buying other people's scrapbooks on eBay. "They're emotionally very moving objects to look at, like visual autobiographies," she said.

One of Scotland's very few specialist trade card dealers is a woman.

"I've always collected things and I always liked bubblegum cards," says Nancy Dewar, whose shop Classic Trading Cards can be found up a stair in Glasgow's St Enoch Square. She used to work in the wages department at Strathclyde Regional Council and turned her hobby into a business 10 years ago when she was made redundant. She is now 60.

She reckons there are probably as many females as males who collect cards, particularly newer sets such as those for the TV series Buffy, Angel and Charmed.

The practice of giving away picture cards as a marketing inducement dates back to the late nineteenth century. Cigarette companies used pieces of card as "stiffeners" in their paper packets and someone came up with the idea putting pictures on them. Cards were also given away with tea and other products.

Cards used photographic images and original artwork, which was often more controversial, particularly that of the American Norman Saunders, one of the main artists on Mars Attacks, an original gum card concept, issued in the US in 1962.

There was widespread criticism of the cards, which feature Martians with frightening skull-like faces and exposed brains. One shows a pet dog being zapped by a Martian ray-gun.

Worried about its established trade in baseball cards, the manufacturer withdrew Mars Attacks. But it remains the most celebrated and iconic bubblegum series of all and was turned into a feature film with Jack Nicholson. Sets sell for £1000 and up.

Saunders managed to get away with just as much blood and gore in the Civil War set - probably the most memorable card is "Painful Death", which shows a soldier fallen from his horse and impaled on a wooden spike.

My own interest was fuelled initially by nostalgia and a continuing enthusiasm for Bond, Beatles and other pop cultural phenomena of my youth. It seems I am not alone. "There's a lot of people who collected them when they were teenagers or kids and as 50-year-olds have gone back to the hobby," says Ian Laker.

Cards offer an opportunity to buy a little bit of pop culture. The price of old cards reflects scarcity, subject matter and the quality of the artwork. But recent issues are unlikely ever to fetch the sort of prices secured by Honus Wagner and even Civil War gum cards.