Free radicals are short-lived, highly reactive open-shell species. They play important roles in a wide range of reactive environments (combustion, atmosphere, plasmas, and interstellar). Studies of free radical photodissociation probe electronic structures and multiple potential energy surfaces (PES's) of the open-shell species, as well as their influences on chemical dynamics and dissociation pathways. This talk will discuss our recent studies on a series of polyatomic free radicals (alkyl radicals, aromatic radicals, etc.).