A method for labelling 6,7-dichloro-2,3-dihydroxyquinoxaline (DCQX) in position 2 with carbon-11 is presented. Diethyl [1-11C]oxalate was synthesized in a two-step, microwave-assisted procedure from no-carrier-added [11C]cyanide and was reacted with 4,5-dichloro-1,2-phenylenediamine in sulfuric acid at 150°C for 10 min. [2-11C]DCQX, isolated by semi-preparative HPLC, was > 99% radiochemically pure with a specific activity ranging between 19 - 26 TBq/mmol. The total time of synthesis was 45–55 min and the isolated, decay-corrected yields were on the order of 10%, based on the trapped [11C]cyanide. A PET study of its biodistribution after intravenous injection in a male rat revealed that the extraction of [2−11C]DCQX across the intact blood-brain barrier was ⩽ 2%.