There is no major difference. You can use a regular mattress on a bunk bed. Where there could feasibly be a difference is in the mattress supplied with the bunk bed and the mattress you use on your regular bed. You often find that the mattress that comes with a bunk bed is thin and of low quality. That’s why we recommend that you try the supplied mattress first, and then change it if you think it is too soft or too thin.