A 13-year-old girl presented in our unit with progressive alopecia and a long history of edematous scalp in the occiput. Biopsy specimen of a lesion showed two-type pathologic abnormality consisting of diffuse neurofibroma in the lower portion and trichotillomania in the upper portion. Since the tumor spread diffusely through the lower dermis and subcutaneous fat tissue without destroying surrounding structures, we concluded that the trichotillomania might result from repetitive scratching or other traumatic behavior at the same site of underlying diffuse nerurofibroma. We reported a case of the concomitant occurrence of trichotillomania associated with diffuse neurofibroma. (Korean J Dermatol 2001;39(10): 1152-1256)