The consequences of decarburization on the creep properties of 2.25 Cr—1 Mo steel have been analyzed. First, a relationship between the creep rate and the carbon concentration as a function of temperature and stress is developed. Then, using this relationship in conjunction with decarburization models developed, creep deformations under typical operating conditions of the steam generator tubings for realistic and pessimistic rates of decarburization are calculated. The results obtained show that the effect of decarburization on the creep deformation level is a function of the operating temperature and the tube dimensions. However, creep deformations remain limited, principally due to redistribution of effective stresses across the tube wall and the fact that stresses are lower on the sodium side where decarburization is more important.