The present invention relates to diagnostic imaging agents for in vivo imaging. The imaging agents comprise a synthetic caspase-3 inhibitor labelled with an imaging moiety suitable for diagnostic imaging in vivo. The invention also provides pharmaceutical and radiopharmaceutical compositions comprising the imaging agents, together with kits for the preparation of the radiopharmaceuticals. Also described are chelator conjugates of the caspase-3 inhibitor, which are suitable for the preparation of imaging agents comprising a radioactive or paramagnetic metal ion. The imaging agents are useful for the diagnostic imaging and or therapy monitoring in vivo of various disease states where caspase-3 is involved.
