I have never seen a scanner that does two-sided in one pass. Everything I have seen is two passes—even those super fancy Xerox and Canon document management devices do one side, put the papers in a tray, and auto-feed the second side. And the cheapies make you turn the sheets over yourself. MY HP all-in-one, as good as it is, makes me flip the pages over to get the back side of each page. Good luck.