Does a chapter published in a book fit as part of a paper-based dissertation? I've just received an offer to write a chapter for a book that will be published with an important publisher. I was about to say yes, because the topic fits with my dissertation topic and I thought I could use it for my paper-based dissertation, but a colleague told me that a chapter in a book may not be considered for a paper-based dissertation. What was your experience? Do you know anything about it? 

Update: Finally my Uni will accept a book chapter as part of my paper-based dissertation. I had to argue that even though it was a book and not a journal, the chapter (actually the whole book) will be reviewed by at least two reviewers. Thanks for your answers!
While regulations may differ from place to place, I find it highly unsurprising that a book chapter would not "count" for a paper-based dissertation.  The reason is that book chapters are typically peer reviewed lightly, if at all.

As such, if your dissertation requirement is effectively "N peer-reviewed papers," then this book chapter is highly unlikely to be peer-reviewed in a manner consistent with the expectations of the university.  Just in the same way, your professors would probably not count a paper in a predatory journal as helping to meet your dissertation requirements.

Note, however, that this doesn't mean you should not write the chapter, if it is a good publisher and a work you would like to create.  Book chapters can be a good way to organize your thoughts and put together reviews, and in some cases can actually be quite highly cited.  Likewise, the text from the chapter may turn out to be useful as part of your dissertation (depending on university regulations about copyright and theses, of course).  It's just that it's probably not a peer-reviewed publication and will thus likely not count toward the number of such that you need for your dissertation.