The role of fluorodeoxyglucose positron emission tomography (FDG PET) in the diagnostic localization of infectious diseases has expanded rapidly in years. In general, sensitivity of FDG PET in depicting infections compares favorably to other diagnostic modalities . It is shown to be useful in patients with suspected osteomyelitis, especially in chronic low grade infections and in vertebral osteomyelitis. although the sensitivity of FDG PET in prosthetic joint infections is very high, reported specificity varies considerably. In experienced centers, FDG uptake localized along the interface between bone and prosthesis can be used to diagnose infection with acceptable specificity. Combined leukocyte scintigraphy and bone scanning, however, remains the standard scintigraphic method for diagnosis of infected joint prostheses. FDG PET has shown promising results in vascular graft infections, in the evaluation of metastatic infectious foci inpatients with blood stream infections and in neutropenic patients, but further studies are needed before definitive conclusions can be drawn . In fever of unknown origin (FUO), FDG PET appears to be of great advantage as malignancy, inflammation and infection can be detected. Image fusion combining PET and computed tomography facilitates anatomical localization of increased FDG uptake and better guiding for further diagnostic tests to achieve a final diagnosis. In conclusion, the body of evidence on utility of FDG PET in infectious diseases and FUO is growing and FDG PET may become one of the preferred diagnostic procedures for many of these diseases, especially when a definite diagnosis cannot easily be achieved.