This paper reports on the reconstitution of reactor pressure vessel steel specimens with CO²-laser beam welding. Experiments were carried out using a 45 kW continuous wave (CW) CO²-laser with a power that varied between 9 to 32 kW. and a welding speed from 1 m/min to 5 m/min. The ability to weld pressure vessel steel by CW CO²-laser was investigated on 18MND5 steel. The laser welding parameters were optimised in accordance with the EN ISO 13919-1 standard. Qualification was performed and a procedure for reconstituting Charpy-V specimens by laser welding is established. Temperature measurements show rapid heating and cooling during the laser welding process. The maximum temperature is about 430°C at a distance of 2 mm from the weld joint and less than 300°C at a distance above 3.5 mm. Static three-point bend tests on un-notched specimens show good resistance of the weld in accordance to the RESQUE-procedure. Reconstituted Charpy-V specimens were impact tested and the results are in good agreement with non-reconstituted specimens.