Neurofibromatosis type 1 is characterized by cutaneous neurofibromas and pigmented lesions of the skin called café au lait spots. Although neurofibromatosis type 1 represents a major risk factor for the development of malignancy, especially of nervous system tumors, malignant lymphoma rarely occurs in a patients with neurofibromatosis type 1. Recently, a 77-year-old woman with neurofibromatosis type 1 was diagnosed as non-Hodgkin's Lymphoma (diffuse large B cell). She had multiple café au lait spots, neurofibromas and right axillary lymph node enlargement. An abdominal CT scan demonstrated a left pelvic mass and para-aortic lymphadenopathy. Because non-Hodgkin's Lymphoma in a neurofibromatosis patient has never been reported in Korea, herein, we describe this case and include a review of the literature.