A toddler with neurofibromatosis type 1 (NF1) was evaluated for tuberculosis (TB) after exposure. Chest X-ray (CXR) revealed a mediastinal mass indicating lymphadenopathy. However, magnetic resonance imaging showed a large plexiform thoracic neurofibroma. CXR performed for TB screening in NF1 patients cannot clearly differentiate lymphadenopathy from thoracic plexiform neurofibroma. Cross sectional imaging is therefore indicated for classification of mediastinal masses.