Overexpressed neuropeptide receptors allow tumor visualization using e.g. radiolabeled peptidic receptor ligands and positron emission tomography (PET) or single photon emission computed tomography (SPECT). This review summarizes the development of radiolabeled probes for peptide receptor imaging since the emergence of the technology with a particular focus on peptide radiopharmaceuticals developed during the last 5 years, and highlights the different factors which are decisive during the process of tracer development and evaluation.