Nuclear Medicine multimodality imaging, such as positron emission tomography/computed tomography PET/CT, refers to metabolic tissue characteristics integrated with anatomical details. Fluorine-18-fluorodeoxyglucose (18F-FDG) is the most diffuse radiopharmaceutical and its application is spreading beyond the area of oncology. The causes of high 18F-FDG uptake that were once considered false positives have been identified and the new knowledge about them led to non-cancerous pathologies that can be studied by 18F-FDG PET/CT. This technique, due to the inflammatory cells high avidity of 18F-FDG, can be useful in studying a variety of inflammatory and infectious systemic conditions. Studies performed in patients with fever of unknown origin (FUO) indicate that 18F-FDG PET/CT offer a great advantage of detecting malignancy, inflammation and infection at the same time both in adults and children. Furthermore, the 18F-FDG PET/CT has proved useful in the study of specific organs such as the heart and brain that represent separate topics also for the development of new specific radiopharmaceuticals. In all the non-oncologic conditions 18F-FDG PET/CT imaging may offer an "all-in-one" procedure, thanks also to its panoramic whole-body acquisition, as an alternative to other diagnostic procedures, reducing the number of unnecessary investigations. The 18F-FDG PET/CT finding of the simultaneous presence of radiopharmaceutical uptake for multiple disease interconnect to different medical disciplines. It is important to describe unexpected occasional typical or atypical PET/CT findings to the growth of scientific and medical community; it can be the starting point to the enlargement of PET/CT indications for a better and wider comprehension of the human system. To recognize unexpected occasional findings is very important a well knowledge of many aspects: physiological biodistribution, diagnostic imaging instrumentations and techniques, pathological aspects of the different neoplastic diseases, patient story, such as previous therapy, and its comorbidity. An unexpected occasional finding can lead to suggest further tests or investigations in order to have a wider comprehension of patients' clinical situation and they are easily explainable when we have a physician's approach towards patient.