PET is recognized as a powerful imaging research tool. Its clinical application has been increasing significantly in recent years. Based on pathophysiological and biochemical principles, functional PET imaging makes it possible to assess parameters of tumor biology not easily accessible to conventional imaging, such as metabolic activity, proliferation, adrenergic transmitter uptake or accumulation of cytostatics in individual tumor manifestations. For clinical application, PET imaging with 2-[F-18]fluorodeoxyglucose (FDG) is of paramount importance. This article reviews recent developments in the use of PET in the diagnosis of abdominal malignant tumors. Diagnosis of pancreatic carcinoma and related liver metastases, locoregional and distant recurrence, as well as therapy control of colorectal cancer, nodal and extranodal staging and therapy monitoring of malignant lymphoma, can be reliably performed with PET. Several appropriately labeled adrenergic transmitters are currently being developed for specific imaging of neuroendocrine tumors. Radiolabeled cytostatics such as F-18 5-FU will shortly be available for clinical use as probes for primary or secondary cytostatic resistance. Encouraging clinical results and attractive new imaging concepts promise increasing use and importance for PET for imaging of abdominal malignancies.