Two cases of rheumatoid nodules evaluated by fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) and video-assisted thoracic surgery (VATS) biopsy are reported. The first case was that of a 44-year-old woman who presented with a cavitated nodule with intense standardized uptake values (SUVs) both in the early (max 3.4) and delayed (max 4.4) phases, suggesting malignancy. However, after VATS biopsy, she was diagnosed as having a rheumatoid nodule with vasculitis. The second case was that of a 74-year-old woman admitted with bilateral lung nodules, two of which showed intense early (max 2.2) and delayed (max 6.0) phase SUVs, and mild early (max 0.6) and delayed (max 0.9) phase SUVs. These two nodules were finally proven to be a lung cancer and rheumatoid nodule without vasculitis, respectively. These cases show that rheumatoid nodules with an enhanced inflammatory process, such as vasculitis, can appear false-positive for malignancy on FDG-PET/CT scan images.