Although uncommon, sinonasal malignancies and aggressive inflammatory processes are entities every radiologist will encounter during the evaluation of routine sinus imaging studies. A high index of suspicion is necessary for prompt diagnosis. It is important to consider aggressive inflammatory disease in all patients having routine sinus computed tomography because any delay in diagnosis can adversely affect the patients’ care. Magnetic resonance (MR) will often provide a better assessment of the lesion extent, allowing for better surgical treatment. MR is crucial for the accurate assessment of neoplastic lesions. A proficient understanding of the complex anatomy of the region is essential.