Abstract: The present invention relates to methods for labeling a PSMA binding ligand with a radioactive isotope, preferably 68Ga, 67Ga or 64Cu, said method comprising the steps of: i. providing a single vial comprising, in dried form, said PSMA binding ligand f the following formula (I): (I) at least one buffering agent, sodium chloride and a stabilizer against radiolytic degradation, ii. adding a solution of said radioactive isotope into said single vial, thereby obtaining a solution of said PSMA binding ligand of formula (I) with said radioactive isotope, iii. mixing the solution obtained in ii., and incubating it for a sufficient period of time for obtaining said PSMA binding ligand labelled with said radioactive isotope, and, iv. optionally, adjusting the pH of the solution.