A carbon-11 labeled benzothiazine calcium antagonist, (+)-(R)-2-[5-methoxy-2-[3-[methyl[2-[(3,4- methylenedioxy)phenoxy]ethyl]amino]propoxy]phenyl]-4-methyl-2H-1,4- benzothiazin-3(4H)-one (semotiadil), and its enantiomer were prepared by N-methylation of the corresponding norderivatives with 11CH3I: decay-corrected radiochemical yields of 16-27% based on 11CH3I, radiochemical, chemical and optical purity of > 99%, sp. act. of 11-50 GBq/mumol and preparation time of 35-40 min. In mice, saturable and stereo-selective uptake in the hippocampus, striatum and hypothalamus was observed. The potential of the compound to visualize the regional brain calcium channels in vivo by positron emission tomography was indicated; however, no promising sign was found in the myocardium.