The magnetic pull of a toyshop is a standard childhood memory. And an early passion for Lego, Action Man or Barbie never quite fades. So it is not surprising that collectible toys are a prime investment, with select examples realising very grown-up prices at auction.

A white Steiff teddy bear from 1925, for example, fetched £25,200 – more than five times estimate – at Bonham's in 2006. Vectis Toy Auctions, meanwhile, the largest specialist firm, recently held a four-day sale realising in excess of half a million pounds.

Despite these huge figures, many toys tumble in value. As in all areas of investment, research is essential. "We've seen no slackening in prices for the best quality stuff and putting money into toys is a great way to diversify in a crunch," says David Nathan, of Vectis. "The risk factor is, however, much higher than, say, putting cash into the Halifax.

With this caveat, he adds that a good portfolio of toys would have brought an "incredible" average annual return of 15 per cent over 20 to 30 years. "We have clients who put £150 a month into recommended toys instead of a pension."

He says that older items – typically pre-1970s – are the safest bet, provided they are in mint condition and boxed. “Some new toys will rocket in price; most won't. It is hard to make that call. With older items, you know whether or not there is a market. Even so, trends come and go. Antique dolls are weak at the moment, while teddies are strong, for example."

He adds: "One definite no-no should be all new limited-edition toys. Buyers almost always keep them in cabinets or whatever, so a perfect example is nothing rare. In contrast, 99 per cent of ordinary toys get play-worn, which means the boxed ones are special."

Popular older items currently include diecast toys by Dinky, Mathbox and Corgi, lead soldiers by Britains and teddy bears from Steiff. Big names are no guarantee of profit, however. "Many post-War Matchbox cars are worth from £50 to thousands of pounds," says Mr Nathan. "But cars from the company's 'Models of Yesteryear' range – made at the same time – are worth a few pounds each.

Toys tied to films, television series or other areas of popular culture are often among the best bets, provided they are originals, issued on or soon after a film, series or record's release. Corgi's 1965 Aston Martin DB5, complete with bullet shield and working ejector seat fetches several hundred pounds mint, while early Star Wars action figures sell for thousands.

Picking the right toy needn't be a struggle. Vectis offers free investment advice to “serious” buyers. Other sources of information include books from reputable publishers, such as Miller's Collectables Price Guide 2008 from Dorling Kindersley, and recent sale prices, available from auction houses. The internet also has plenty of sites with information on toys, but that these should be used with caution – most are the work of amateurs and some are years out of date.

Investors should be equally careful buying online. Vectis and a number of the big-name London auctioneers now allow people to bid for toys at their websites. These are safe, although it is best to view an item before purchase wherever possible. Purchasing from many other websites, especially those based overseas, carries significant risk, however. GetSafeOnline.org, a Government portal, has advice on minimising this, with videos on "buying safely on eBay", for example.

If you are buying as an investor, you will sooner or later come to sell. Remember not to take recent sale prices as a guide to what you will make on an item. Auctions take from around 20 per cent of the hammer price in commission and charges. Dealers, meanwhile, pay around half to two thirds of the amount they hope to sell an item on for. Even eBay exacts a seller's fee on each transaction – recently raised from 5.25 to 7.5 per cent of the sale price.

Children's books are an easy to keep alternative collectible to toys. Kate Bliss, an independent fine art value and expert on the BBC's Bargain Hunt says that "classics such as Eric Hill’s Spot books and Rod Campbell’s Dear Zoo", available in bookshops from £4.99 should be worth three to four times their price - taking inflation into account - by 2030. Hatchard's, of Picadilly, has a selection of signed first editions, some of which could make far greater gains, Harry Potter-style.