This article presents some anatomic and neuroradiologic clues in the identification of intrinsic tectal tumours and the main related problems of differential diagnosis. The majority of intrinsic tectal lesions are low-grade gliomas that have been recognized as a potential cause of late-onset aqueductal stenosis. The superb sensitivity of magnetic resonance (MR) imaging and its multiplanar imaging capability allow an optimal diagnostic accuracy in the tectal region. For this reason, MR imaging should be included in the work-up of all patients with neurological findings of brain stem dysfunction and late-onset aqueductal stenosis. Tectal gliomas particularly merit an accurate MR long-term follow-up monitoring, since they may ultimately show evidence of progressive growth and require therapeutic intervention to maintain disease control.