Purpose: Diffusion magnetic resonance imaging (MRI) and 6-[18F]fluoro-l-dopa ([18F]FDOPA) positron emission tomography (PET) are used to interrogate malignant tumor microenvironment. It remains unclear whether there is a relationship between [18F]FDOPA uptake, diffusion MRI estimates of apparent diffusion coefficient (ADC), and mitotic activity in the context of recurrent malignant gliomas, where the tumor may be confounded by the effects of therapy. The purpose of the current study is to determine whether there is a correlation between these imaging techniques and mitotic activity in malignant gliomas.Procedures: We retrospectively examined 29 patients with recurrent malignant gliomas who underwent structural MRI, diffusion MRI, and [18F]FDOPA PET prior to surgical resection. Qualitative associations were noted, and quantitative voxel-wise and median measurement correlations between [18F]FDOPA PET, ADC, and mitotic index were performed.Results: Areas of high [18F]FDOPA uptake exhibited low ADC and areas of hyperintensity T2/fluid-attenuated inversion recovery (FLAIR) with low [18F]FDOPA uptake exhibited high ADC. There was a significant inverse voxel-wise correlation between [18F]FDOPA and ADC for all patients. Median [18F]FDOPA uptake and median ADC also showed a significant inverse correlation. Median [18F]FDOPA uptake was positively correlated, and median ADC was inversely correlated with mitotic index from resected tumor tissue.Conclusions: A significant association may exist between [18F]FDOPA uptake, diffusion MRI, and mitotic activity in recurrent malignant gliomas.