I watched Hunter x Hunter anime show some time ago.
So my question is, are the manga much better than the anime or is the story any different? If not, which chapter does the manga separate from anime ?

I don't know what part of the anime did you watch. (does that include the 3 OVA's or not etc...)
But you know... you can use the information on the series info page at:

Anime Start/End Chapter
Ends at Vol 18,Chap 185

And just to note I'm not sure about this, but I don't think there are that much differences between the manga and anime for the entire part covered by the anime.
The manga was in hiatus up to now, but it should get back on track in October apparently, which is rather good news.

its a litlle bit different but not so much, the test and somethings changes but nothing else

If you want to know about HxH then you should check out this site. They have everything to do with Hxh.
http://groups.msn.com/HxHrevamp/yourwebpage.msnw

Ok thx for answers. I guess i start read from vol 18 then...
too lazy to start from chapter 1 ^^

You should also know that they art starts to get a lot worse after the Greed Island arc..

Quote from ikuyoK

You should also know that they art starts to get a lot worse after the Greed Island arc..

Again, for the umpteenth time: The art gets redrawn when published in book-form.

I just meant what he will read.. At least all the ones I read after were like that..

Quote from ikuyoK

I just meant what he will read.. At least all the ones I read after were like that..

Second versions have been released of redrawn volumes.
If you download them again, you'll get the improved art for volumes 20 and up iirc.

%90 manga always better than anime
in the manga
gon more evil
sometimes he just dont give a fuck about everything