Primary central nervous system lymphoma (PCNSL) is rare neoplasm, affecting both immunocompetent and immunodeficient patients. It is usually seen as intracranial tumor, but it can often involve cerebrospinal meninges, eyeballs and spinal cord. Although PCNSL is sensitive both to radiotheraphy and chemotheraphy, it's recurrences are very frequent. Mean survival time does not exceed several months. We described a case of 43 year old patient with diagnosed PCNSL and discussed clinical signs, diagnostics and treatment of the neoplasm. In our case report we emphasized transient remission after treatment with corticosteroids, which delayed a correct diagnosis and worsened final prognosis.