Conventional plain-film radiography may be used as a screening method for various pathological conditions of the sinonasal cavities. However, CT scanning remains the study of choice for the imaging evaluation of acute and chronic inflammatory diseases of sinonasal cavities. MRI is superior to CT in differentiating inflammatory conditions from neoplastic processes. The most common complications of rhinosinusitis in children occur in the orbit. The information obtained from the CT scan and MRI, together with clinical findings, may be the best guidelines for clinical management and the mode of treatment. Although intracranial complications of sinusitis are relatively rare, prompt recognition of these disease states is important to prevent permanent neurological deficit or fatality. It is prudent to obtain MRI of the sinuses, orbits, and brain whenever extensive or multiple complications of sinusitis are suspected, in addition to CT scanning. Chronic rhinosinusitis is a clinical diagnosis, confirmed and staged with the CT scan of sinonasal cavities. Chronic inflammatory disease is often associated with mucosal thickening and sclerosis of the bone, particularly within the sinuses. Chronic extramucosal fungal sinusitis develops as a saprophytic growth in retained secretions in a sinus cavity. The imaging manifestations of chronic mycotic rhinosinusitis may be nonspecific or highly suggestive of the presence of fungal infection. The presence of diffuse increased attenuation within the paranasal sinuses and nasal cavity should be considered as chronic allergic hypersensitivity aspergillosis (chronic noninvasive aspergillosis) or chronic hyperplastic sinusitis and polyposis associated with desiccated, retained mucosal secretions. The MRI characteristics of fungal sinusitis depend on the stage of the disease.