The present application discloses compositions and methods of synthesis and use of F-18 labeled molecules of use in PET imaging. In particular embodiments, the labeled molecules may be peptides or proteins, although other types of molecules may be labeled and utilized. Preferably, the F-18 is attached to a targeting molecule by formation of a metal complex and binding of the F-18-metal complex to a chelating moiety. In other embodiments, the metal may first be attached to the chelating group and subsequently the F-18 bound to the metal. More preferably, the F-18 label moiety may be attached to a targetable conjugate that is used for pretargeting in combination with a bispecific or multispecific antibody. The F-18-metal labeled molecules are stable in human serum at 37° C.