I am being offered a PhD studentship in the field I am interested but the precise topic of research is different from my interests.
The project in question is industry specific. I prefer to work on a project thats different but requires same techniques and theory (ie its aimed at another industrial product). If I refuse now, I might have to wait a year or two.
Should I take it? Will it make any difference, if, later I look for a post-doc (in the same field) but a different topic.

Hi - in my experience (and I'm from Arts, so this may not be relevant), they let you "tailor" your PhD to your own interests, I guess so that you keep your interest levels up, and not quit the project, especially if it's quite similar. It's probably best talking to the supervisor of the project though as they will know what exactly they want from the project, and if "tailoring" to suit your needs is possible.

That's what I want to know. I'm interested in a particular technique but there aren't many projects in that area. What if I got a project using a similar technique (i.e. in that field with same theory etc)but different technique - will that affect what my choices are afterwards if I want to go back to original technique?