String Suffix Automata and Subtree Pushdown Automata. Abstract: String suffix automata accept all suffixes of a given string and belong to the fundamental stringology principles. Extending their transitions by specific pushdown operations results in new subtree pushdown automata, which accept all subtrees of a given subject tree in prefix notation and are analogous to the suffix automata in their properties. The deterministic subtree pushdown automaton accepts an input subtree in time linear to the number of nodes of the subtree and its total size is linear to the number of nodes of the given subject tree.