The transient photochemistry of diflunisal has been investigated in aqueous solution. The photoreactivity of the compound is quite unusual for fluorinated derivatives. The loss of fluoride does not occur from an excited state, as expected, but is photostimulated through a reaction involving trapping by the ground state of electrons photoejected from diflunisal. Mono- and biphotonic pathways are involved in the photoionization process. A phenoxy radical generated after photoionization has been characterized as the main transient species involved in the photodegradation. A cross combination reaction between phenoxy and aryl radicals is controlled by the persistent radical effect and is responsible for the formation of the stable photoproduct.