Technologies are described herein for classifying structured documents based on the structure of the document. A structured document is received, and the structural elements are parsed from the document to generate a text string representing the structure of the document instead of the semantic textual content of the document. The text string may be broken into N-grams utilizing a sliding window, and a classifier trained from similar structured documents labeled as belonging to one of a number of document classes is utilized to determine a probability that the document belongs to each of the document classes based on the N-grams.