The development of L-DOPA-induced dyskinesia (LID) is one of the most severe side effects of chronic L-DOPA treatment in Parkinson's disease patients. [11C]DASB positron emission tomography (PET) provides a prominent tool to visualize and quantify serotonin transporter (SERT) pathology in vivo in patients and in animal models. To evaluate the effect of chronic L-DOPA treatment on SERT availability in an animal model of LID, we performed a longitudinal PET study.