The invention relates to stabilised radiopharmaceutical compositions which comprise: (i) an 18F-labelled compound； (ii) an effective stabilizing amount of gentisic acid or a salt thereof with a biocompatible cation； (iii) an aqueous biocompatible carrier medium； wherein the radioactive concentration of the 18F in the carrier medium is in the range 10 to 100,000 MBq/ml and the pH of the composition is in the range 4.0 to 9.5. The invention further comprises methods for preparing such radiopharmaceutical compositions and a new use of gentisic acid or a salt thereof.
