Whereas in the past the term "vasculitis" was most frequently used in context with systemic vasculitides, such as the large vessel vasculitides (LVV) Takayasa arteritis and giant cell arteritis, characterized by inflammation of blood vessel walls, it nowadays comprises also inflammatory changes of the vessel wall as a substantial part of the atherosclerotic disease process. Implementing non-invasive imaging techniques, such as computed tomography angiography (CTA), magnetic resonance angiography (MRA) as well as positron emission tomography (PET) in the diagnostic algorithm of atherosclerosis and LVV, depicts a promising step towards an earlier detection with a, consecutively, improved therapeutic approach and potentially prognostic benefit in patients suffering from vasculitis. Mainly molecular imaging with 18F-fluorodeoxyglucose (FDG) PET seems to be promising in offering an early and sensitive identification of inflammatory changes in both, atherosclerosis and LVV. This review will therefore provide an overview on the diagnostic performance and clinical relevance of FDG-PET in monitoring vasculitis in atherosclerosis and LVV, with a focus on LVV.