Substituted aryl-boron compounds comprising at least one 18F atom, as illustrated by the formula (I), where at least one of Y1 or Y2 is 18F and A1 is a substituted aromatic ring, with G1-5 being, independently, C or N, and where the substitutents of the aromatic ring or polycyclic moiety (other than boron) comprise at least one electron-withdrawing group (EWG), providing that sigma total (σtotal) for all substituents on the aromatic ring or polycyclic moiety except B is about 0.06 or more when said at least one EWG is positioned ortho to B, or about 0.2 or more when no EWG is positioned ortho to B. The compounds include neutral (N=1) and ionic borate (N=2) embodiments. The compounds are useful as positron emission tomography (PET) imaging agents.