Any non-synchronous DC/DC converter requires a so-called freewheeling diode. To optimize overall solution efficiency, one typically tends to choose a low forward voltage Schottky. In many cases, the design uses a diode that is recommended by the (web-based) tool used to design the converter. This does not always result in the most optimal diode choice. If a design tool does not consider the dynamics between thermal and leakage behavior, actual performance can be very different from what is shown in a design-tool analysis or simulation. This paper will discuss some of the typical parameters that should be examined in order to make a correct diode selection.