The present invention relates to novel radiolabelled inhibitors of general formula I for the Glycine 1 transporter (GlyT1), useful for the labelling and diagnostic imaging of the glycine 1 transporter functionality.wherein R1is isopropoxy or 2,2,2-trifluoro-1-methyl-ethoxyand R2is a radiolabelled group CH3, wherein the radionuclide is3H or11C. It has been found that the radiolabelled compounds of formula I may be used as PET (PositronEmissionTomography) radiotracer for the labelling and diagnostic molecular imaging of the glycine 1 transporter functionality.本發明係有關一種甘胺酸1轉運子(GlyT1)之具有通式I之新穎放射性標幟抑制劑,其適用於標幟及診斷性顯像甘胺酸1轉運子功能性。其中R1 係異丙氧基或2,2,2-三氟-1-甲基-乙氧基;及R2 係放射性標幟基團CH3,其中放射核種為3H或11C。已發現具有式I之放射性標幟化合物可用作PET(正電子發射斷層攝影術)放射性示蹤劑,以標幟及診斷性分子顯像甘胺酸I轉運子功能性。