[18F]exendin-4 is a radioligand specific for the gluca- gon like peptide-1 receptor (GLP-1R) abundantly expressed in beta cells. Quantitative non-invasive PET (positron emission tomography) imaging of pancreatic beta cells would serve as a valuable diagnostic tool and provide means to monitor therapeutic interventions. Several exendin based tracers have been intensively explored for beta cell imaging. The obstacle with these has been high uptake in the kidneys. The aim of this study is to develop a novel [18F]exendin-4 tracer for clinical imaging of beta cells with PET.