L-[3-18F]-α–methyltyrosine (FMT) is amino-acid tracer for positron emission tomography (PET), and is used for tumor detection because malignant tumor cells accumulate 18F-FMT based on the increased expression of amino-acid transporter. This study was conducted to investigate a usefulness of 18F-FMT PET in combination with 18F-FDG PET for the diagnosis of sarcoidosis in patients with suspected malignancy.