A 64-year-old woman was admitted to our hospital for further examination of an abnormal shadow in the left lung, that had grown slowly for 9 years. Bronchial brushing cytology was performed under bronchoscopy, but was negative for malignancy and for other significant findings. 11C-Choline-positron emission tomography (11C-Choline-PET) showed medium-level uptake in the mass lesion in the S 6 lobe of the left lung, but 18F-fluorodeoxyglucose-positron emission tomography (18FDG-PET) did not yield any such result. These findings suggested the presence of a slowly growing benign tumor, or a neoplastic disease, such as a potentially malignant tumor or a low-grade malignancy. To arrive at a diagnosis, a left partial lobectomy was performed on January 29, 2001. The microscopic findings of this mass lesion showed a solid, hemorrhagic pattern; papillary projections into spaces covered or lined by cuboidal cells, and sheets of round to polygonal cells. The histological diagnosis of this tumor was a sclerosing hemangioma. Recently, 18FDG-PET has been proven to be a clinically useful tool for the detection and staging of malignant tumors, and the follow-up of malignant diseases after treatment; while 11C-choline was recently reported to be a new PET tracer used to visualize various malignancies. The uptake of 11C-choline in tumors represents the rate of tumor cell duplication. It is suggested that 11C-choline-PET may be useful in the diagnosis of sclerosing hemangioma, as in this case.