Three experiments tested the main claims of the idiom decomposition hypothesis: People have clear intuitions on the semantic compositionality of idiomatic expressions, which determines the syntactic behavior of these expressions and how they are recognized. Experiment 1 showed that intuitions are clear only for a very restricted number of expressions, but for the majority of idioms, they are not consistent across speakers. Experiment 2 failed to support the claim that semantic compositionality influences the syntactic flexibility of idioms. Finally, Experiment 3 showed that idioms are more quickly recognized than their literal counterparts, regardless of compositionality and syntactic flexibility. All of the findings were at odds with the tenets of the idiom decomposition hypothesis. The theoretical implications of the results with respect to idiom processing and the notion of compositionality are discussed.