The invention provides a composition of matter of formula I V-L-R (I) where V is an organic group having binding affinity for an angiotensin II receptor site, L is a linker moiety or a bond, and R is a moiety detectable in in vivo imaging of a human or animal body, with the provisos that where V is angiotensin or a peptidic angiotensin derivative or analog then V-L-R is other than a non-metal radionuclide substituted peptide (eg .sup.125I substituted angiotensin II) and L-V is other than simply a peptide with a chelating agent amide bonded to a side chain thereof. This composition of matter may be used to image cardiovascular diseases and disorders.