Last year a poster for the 1933 film The Mummy, starring Boris Karloff, sold for $450,000 (pounds 275,000) and before that the record was held by a Toulouse Lautrec that went for pounds 250,000.
The demand has increased dramatically over recent years, which prompted Christie's to begin having twice-yearly auctions in 1995. The star of its show is undoubtedly going to be The Invisible Man, which is likely to fetch between pounds 30,000 and pounds 50,000.
Sarah Hodgson, a Christie's consultant, says: "We used to include film posters as part of a general entertainment sale, but it just seemed to take off. The prices are going up, but it's still one of those areas of the market where you can get cheap things."
Tony Nourmand, the co-owner of The Reel Gallery, a film poster gallery, and a consultant to Christie's, notes: "At least 95 per cent are worth under pounds 500. You can get a lot of good stuff for pounds 500. An original poster for Bullitt, for example, will cost just under pounds 500 - also certain Bond posters, such as You Only Live Twice."
Certain genres are particularly collectable, such as horror and sci-fi, particularly those from the 1930s. The real cream of the crop are posters that were produced by Universal Studios during the Depression, The Invisible Man being a prime example. As always, exclusivity is the key to real worth. In the case of Universal this (at the time) small studio was so strapped for money that very few posters were produced, especially as the studio was hit by a paper strike.
More recent posters that will be in the Christie's sale include those from so-called "Blaxploitation" films of the 1970s, such as Shaft, likely to sell for between pounds 250 and pounds 400. Posters for Grease and Saturday Night Fever are also likely to go for the same price.
New posters can also be worth money. Reprints for Reservoir Dogs have replaced Joy Division and Che Guevara as student posters, but a genuine original of the American version is likely to be worth between pounds 350 and pounds 500.
An original poster is one that has been generated by the film company's publicity department and sent to cinemas, and should not be confused with the thousands of reprints.
In theory you can ask a cinema for its publicity posters after the film has finished and some will comply, but trying to stay ahead of the game with modern films is a bit of a minefield.
Mr Nourmand advises steering clear, and according to Richard Dacre, owner of Flashbacks, a poster shop in London, people can get their fingers burnt because it is much easier to make good replicas of modern posters.
He says: "There's a lot of forgery going on at the moment and Titanic was a particularly notorious case.
"There was a fourth design around for a while that became quite collectable until Fox pointed out that they had never done one!"
He adds: "It's very dodgy going for blockbusters."
how to get started
Do go for films that appeal to you, but the following are all collectable genres: horror, sci-fi, "leading ladies" (Hepburn, Garbo, Dietrich), Cult 1960s and 1970s, Bond films, and British films such as Ealing Comedies or Carry Ons.
Shop around. Look out for Movie Memorabilia fairs.
Contacts: The Reel Gallery, 72, Westbourne Grove, London, W12 55H, 0171- 727 4488; Flashbacks, 6 Silver Place, London W1R 3LJ, 0171-437 8562.