The invention provides peptides that can reactivate p53 mutants efficiently and specifically, as well as methods that allow the identification, selection and isolation of such peptides, in a precise, cost and time effective manner. In particular, there are provided mutant p53 reactivating peptides that can restore the native wild type p53 folding, and hence the tumor suppressor activity, to the mutant p53 protein. Such peptides are useful for treating various conditions and diseases in which p53 is mutated.