The general answer is that a queen bed tends to be a little bit wider and a little bit deeper (taller) than a full mattress. The length of the beds (head to toe) tends to be the same. However, the big difference usually comes in when buying sheets. While, for the most part, a queen sized sheet will fit a full sized bed and vice versa, different brands may have different sizing. If a brand sells only twin, a full/queen, and king sized sheets, you can safely assume that the full/queen will fit both a full and a queen. Some brands do break it down and sell both a full and a queen size. For these brands, you can probably get their queen size to fit your full bed, but you're likely to find the full size sheet to be too small for a queen sized bed.