CONTEXT. Attack treesare a recommended threat modeling tool, but there is no established method to compare them. OBJECTIVE. We aim to establish a method to compare "real" attack trees, based on both the structure of the tree itself and the meaning of the node labels. METHOD. We define four methods of comparison (three novel and one established) and compare them to a dataset of attack trees created from a study run on students (n = 39). These attack trees all follow from the same scenario, but have slightly different labels. RESULTS. We find that applying semantic similarity as a means of comparing node labels is a valid approach. Further, we find that treeedit distance (established) and radical distance (novel) are themost promising methods of comparison in most circumstances. CONCLUSION. We show that these two methods are valid as means of comparing attack trees, and suggest a novel technique for using semantic similarity to compare node labels. We further suggest that these methods can be used to compare attack trees in a real-world scenario, and that they can be used to identify similar attack trees.