Primary non-Hodgkin lymphoma (NHL) of the paranasal sinuses is a rare neoplasm that cannot be easily diagnosed and differentiated as its clinical, histological, and imaging features are similar to those of other inflammatory and tumorous diseases in their early stages. We evaluated the morphological and functional imaging characteristics of primary NHL of the sphenoid sinus using CT and MR imaging. Morphological CT and MR imaging as well as perfusion CT imaging and proton MR spectroscopy (PRESS technique, TE = 135) was performed in three patients with the histological diagnosis of highly malignant primary B cell lymphoma of the sphenoid sinus. In all patients an inhomogeneous contrast agent enhancement as well as bony erosion of the sphenoid sinus was identified in CT and MR sections. In one patient an infiltration of the adjacent dura was present. The mean blood flow of the lymphomas was 135 ml/min per 100 g tissue, the mean blood volume was 8.06 ml/min, while the mean transit time and the mean permeability surface area product values were 5.11 s and 26.53 ml/min per 100 g, respectively. The mean choline to creatine ratio in the proton MR spectroscopy was 5.7. Cross-sectional imaging findings are not sufficient to establish the diagnosis of a primary NHL in the sphenoid sinus. Physiologic imaging offers valuable information that may be characteristic of the tumor. Future studies may lead to a safe differentiation of the lymphomas from other pathologic entities based on the combination of morphological and functional imaging.