Collecting film posters is a huge market, with vintage prints fetching from hundreds to several thousand pounds each.

Ms Sarah Hodgson, a specialist in the entertainment department at Christie's, says the London auction house has sold several film poster collections from Ireland which were collected by managers whose cinemas had closed down. "The world record for a poster is $450,000 (€399,467). That was for a poster called The Mummy, a 1933 horror film from Universal Studios. Universal horror films from that period are some of the most collected posters in the world. They get the highest prices," she says.

Original posters from Hollywood classics like Gone With The Wind, Casablanca and The Wizard of Oz are highly sought after. For example, Christie's sold a US three-sheet (81 by 41 inches) Casablanca poster for £23,000 (€29,204). "These classics were actually released several times by the film companies because they were so popular. So, for example, you may get an original poster for Gone With The Wind from 1939, but it was also released again in 1940 and, I think, again in 1943. "All those posters for those releases can be considered original, but the most valuable is going to be from the first release," she says.

Original cinema posters, that is, the ones that were displayed outside the cinemas, are the valuable ones. Condition is quite important. But readers should be careful of buying reprints, which obviously are not worth anything like the originals. "Usually you can tell by the quality of the paper and also the sizes are sometimes different. Reprints are sometimes smaller, just by a few inches," she says. The standard size on this side of the Atlantic is a quad, that is, 30 inches tall by 40 inches wide. The standard US one-sheet is 41 inches high by 27 inches wide.

"Very often Irish posters have been censored in some way. Like the poster for Dr No, the 1962 James Bond film, has all these women on the poster very scantily clad and every Irish poster I've ever seen has been blacked in with felt pens covering them up. And obviously that devalues posters," she says. The most valuable posters date from the 1930s and 1940s. Very early posters aren't particularly sought after, with the exception of Charlie Chaplin. "His posters are still very sought after. Something like The Kid, one of his most famous films, should fetch £15,000 to £20,000 for an American poster," she says.

The highlight of Christie's vintage film sale on March 22nd next is an unusual poster for the German Expressionist film The Cabinet of Dr Galigari, which has an estimate of £10,000 to £15,000 sterling (€14,492 to €21,739). But the forthcoming auction shows that even some recent film posters can be valuable if they are unusual in some way. For example, an E.T. poster showing Elliot riding his bicycle with E.T. clearly visible in the basket has an estimate of £400 to £600. Apparently, Stephen Spielberg withdrew the poster because he didn't want anyone to see E.T. before they saw the film.

There are also unusual Star Wars film posters in the sale. For example, a Revenge of the Jedi 1982 poster is expected to fetch £300 to £500 - showing the original title for Return of the Jedi.

Meanwhile, a rare Lawrence of Arabia 1962 poster is expected to fetch £3,000 to £5,000, as is a poster of the 1941 film Moon Over Miami. A Frankenstein 1931 poster is estimated at £2,000 to £3,000, while a tenth anniversary poster of the Rocky Horror Picture Show 1985 is expected to fetch £250-£400.