Movie posters have been around for as long as the cinema industry itself. In recent years their value as collectables has increased enormously, as evidenced by the mint condition 1931 Frankenstein poster, which sold for over £90,000 at Sotheby's recently.

Of course, newer movie posters and those which are slightly worn or damaged would hardly climb out of the £20 to £50 price bracket, but still, in quantity they can be quite valuable. 

Few people had the foresight to keep or collect posters advertising the latest film releases in the early years of Hollywood, as they were neither considered artistically important or potentially valuable. Then, during the war years, all spare paper -including posters - was recycled for the war effort, making movie posters from this era especially rare. 

Until the early 1980s, when for-sale poster art became widely accepted, many cinemas either simply destroyed old movie posters, or returned them to the studios with the film, when the run was finished. But once the production studios discovered that there was a retail market for posters, they were quick to begin additional print runs of popular posters for the retail market. Thus, examples from the seventies and earlier are viewed as legitimate investments, while posters from the sixties in particular are today rising in value sharply.

As with many other collectable categories, the rule of thumb is the older the better.  Condition is paramount (if you'll excuse the pun) and both the box-office success of the film and the popularity of the leading actors play a key  role in a poster's likely value. 

For those who are concerned with investment rather than art, a useful tip is to concentrate your search on the early or debut appearances of popular actors. As an actor's reputation and status grows, so too will the value of posters from his or her earlier movies. Just like oil paintings by well-known painters, the artist's (or actor's) death can do wonders for demand and consequently value. 

Mostly, successful investment in this field is down to spotting potential trends before others and  then speculating a little, but it is fairly safe to assume that 'advance' posters, which promote an coming releases, will be worth significantly more as they are usually produced in very small quantities. These can be worth big money if the film subsequently does well at the box office. One famous example of this is the original advance poster for Return of the Jedi, which bore the title Revenge of the Jedi. Only a few bearing this title had been sent out when the studio made a last minute switch and these now sell consistently for over £250. 

If you're on a lower budget, you may be lucky enough to spot an original poster for a cult film, such as the 1982 classic, Blade Runner, now worth up to £100, or try establishing a collection based on Disney productions.  Disney is the only studio that still asks cinemas to return posters once a movie closes and you'll have the added stability of a much wider community of  Disneyana collectors. Values tend to be lower, for example the limited edition Tarzan poster is worth £30 to the right person, but the market is so huge you're unlikely to experience a sudden decline in demand or get stuck with an unsaleable item.