For multi-criteria optimization of radiation therapy treatment planning, several methods can be used. One method, the 2-phase ?-constraint method, is to optimize each criterium, one at a time, to find an optimal radiation plan. The disadvantage of this method is that it takes a lot of computation time. The purpose of this thesis is to investigate a new multi-criteria method, the multiple reference point method, which takes just one optimization. The multiple reference point method is compared with the 2-phase ?-constraint method and with the weighted-sum optimization method with equal weights. This because of the simplicity of this method and because it also takes just one optimization. The multiple reference point method is tested for several test cases, and for five real patients. The plans from the multiple reference point method is for large lists better than the weighted-sum plans with equal weights, and are about as well, and even sometimes better than the plans from the 2-phase ?-constraint method.