Neuronal plasticity is an essential feature of the nervous system in the transfer of pain responses into a state of pathological processing. Indications of neuroplastic changes in the human central nervous system may be derived from positron emission tomo graphy (PET). Previous studies have shown that the neuronal structures involved in the processing of pain have a region specific reduction of opioid receptor binding during ongoing pain and normalized binding after pain treatment. Furthermore, a recently reported study using a ligand labeled with the PET-radionuclide 11C (t<sub>1/2</sub>=20.3 min) demonstrated the significance of focusing on the my-opioid receptor (my-OR) for such studies. The planned project aims to provide my-OR selective ligands based on the radionuclide <sup>18</sup>F (t<sub>1/2</sub>=109.7 min). By the longer half-life f this radionuclide as compared to <sup>11</sup>C, it can be anticipated more flexible clinical proto cols, increased accuracy of the procedures involved and less stresses to the patients. The proposed strategies for the preparation of <sup>18</sup>F-labeled my-selective ligands offer a broad spectrum of potential candidates. It also presents the possibility to vary and adapt the lead structure with respect to optimization of the ligand bin ding properties.