Poly(ADP-ribose) polymerase (PARP) is involved in repair of DNA breaks and is over-expressed in a wide variety of tumors, making PARP an attractive biomarker for positron emission tomography (PET) and single photon emission computed tomography imaging. Consequently, over the past decade, there has been a drive to develop nuclear imaging agents targeting PARP. Here, we report the discovery of a PET tracer that is based on the potent PARP inhibitor olaparib (1). Our lead PET tracer candidate, [18F]20, was synthesized and evaluated as a potential PARP PET radiotracer in mice bearing subcutaneous glioblastoma xenografts using ex vivo biodistribution and PET-magnetic resonance imaging techniques. Results showed that [18F]20 could be produced in a good radioactivity yield and exhibited specific PARP binding allowing visualization of tumors over-expressing PARP. [18F]20 is therefore a potential candidate radiotracer for in vivo PARP PET imaging.