Just want to mention for those looking for an affordable copy of this film, avoid the South Korean dvd offered on ebay, as it is a cut/censored version of "Possession," editing out 5 minutes from the running time. The dvd is also most likely, an unauthorized bootleg. I was suckered by this scam and dont want other fans of this film to be fooled into buying this.
The Korean censorboard is ridiculous, films that are totally harmless are completely banned in Korea. The censoring explains the cheap prices for those dvd´s, and it is too bad, because other than the cutting of scenes the picture and sound quality of these discs are usually very good. Look for Chinese editions; they are usually direct rips from the original, and they are not censored, the only difference is the chinese writing on the box...
I bought one of the korean ones from Ebay, only cost me 4 or 5 quid. Couldn't afford to pay £20 for the right one.
What's missing in those 5 minutes, it doesn't say on IMDB. I know there are extra bits in the subway scene, but I am not sure if they are even on the Anchor Bay one either.
The scenes of sexualized violence have been either cut down or removed. The murders of the men by Adjani are cut down, as is the scene where she has intercourse with the "monster." There is a fine dvd from Anchor Bay, that features Mario Bava's "Shock" on the flipside of "Possession." It is out of print, but you can get lucky and find it second hand on ebay, I think i got mine for about 10 euro. You might be surprised how bloody this strange film really is. And that subway scene is unforgettable.