The present invention provides means, such as a method, for determining whether a mammalian subject having a colorectal cancer belongs to a first or a second group, wherein the prognosis of subjects of the first group is better than the prognosis of subjects of the second group. The method comprises the steps of: evaluating an amount of RBM3 protein or RBM3 mRNA molecule in at least part of a sample earlier obtained from the subject and determining a sample value corresponding to the evaluated amount; comparing said sample value with a predetermined reference value; andif said sample value is higher than said reference value, concluding that the subject belongs to the first group; and if said sample value is lower than or equal to said reference value, concluding that the subject belongs to the second group.