We present three different cases of patients with papilledema: one case with a primary tumour of the optic nerve, and two cases with secondary involvement of the optic nerve (breast carcinoma and non-Hodgkin lymphoma). The visual acuity varies from sudden, painless, decrease of vision, to blurred vision and proptosis on the affected eye. A characteristic ophthalmoscopic examination shows a swollen optic disc and promonence with tortuosity of blood vessels. A fluorescein angiography shows dilated capillaries of the optic disc with leakage in the early phase and diffuse hyperfluorescence during the late phase. A ultrasonography B-scan of the affected eye shows prominent optic nerves with widened optic nerve sheath. An exhaustive history and complete ophthalmological examination are essential for the diagnosis, to which fluorescein angiography, B-scan ultrasonography, ocular coherent tomography, computerized tomography, and magnetic resonance can be used as useful additional tests. Treatment and prognosis depend on the primary process. We emphasize the crucial role of ophthalmologist in the early diagnosis of CNS neoplasia.