We report a case of maxillary sinus (MS) aspergillosis studied by positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) and by 67Ga-citrate (Ga) single photon emission computed tomography (SPECT). The FDG uptake existed in the lesion and along the inflammatory edematous mucous membrane of the MS. Ga uptake occurred not only in the lesion and in the mucous membrane but also in the MS. Relative quantification, the standardized uptake value (SUV) of the lesion showed relatively high FDG uptake (3.7). But in other reports, many malignant head and neck tumors had a SUV below 3.7. It was thought to be difficult to differentiate between aspergillosis and malignant head and neck tumors by FDG-PET.