Diphenyl diselenide (Ph2Se2) is an organoselenium compound. Its crystalline structure, toxicokinetic properties, antioxidant and anti-inflammatory activities have been investigated. Its ability to reverse the oxidative brain damage and mitochondrial dysfunction induced by acetaminophen has been studied in mice. It reacts with thallium (Tl) to form TI (SePh). It participates in a four-component radical coupling to form substituted cyclopentanes.