Unpredictable size of illustrations

My manuscript has a number of illustrations. When I compile to PDF, the illustrations display in exactly the right size. However, when I compile to MOBI or ePub formats, the illustrations seem to be coming out much smaller. They are slightly bigger in ePub compared to MOBI but much smaller than in PDF.

What could be going on here and how can I rectify this?

  • CDM

It might be a good idea to go through some online tutorials or even books on preparing images for publication, and the unique things you will need to keep track of when working on very different “platforms” such as print and e-book publishing. What works well for a printed book may not even function at all on a Kindle, where if you optimise for that, it would be too small in print, and still not work right on a Kobo or Nook.