Positron emission tomography (PET) scans use positrons, positively charged particles, to detect metabolic and chemical changes in the body. Although the clinical applications of this technology still are evolving, PET scans are being used to detect cancer and evaluate neurologic disorders, heart muscle function, and response to treatment. In oncology, PET scans may be used to determine biopsy location, stage disease, diagnose cancer recurrence, and discern malignant from benign conditions. PET scans also have led to the incidental diagnosis of cancer. This article reviews patient preparation and PET scan procedures and includes a patient information sheet on PET scanning. Oncology nurses need to be well informed about new technologies used in cancer care, such as PET scans, to better educate and prepare patients to undergo these tests.