OBJECTIVE: To compare the differences in cerebral oxygenation responses between the infants born preterm and full-term infants and to evaluate the early cognitive ability of infants born preterm. METHODS: Cerebral oxygenation after light stimulation was detected by near infrared spectroscopy (NIRS) in preterm infants at 3 or 6 months corrected gestational age (GA). The results were compared with those of age-matched infants born at term. RESULTS: The start and peak response time of cerebral oxygenation occurring after light stimulation in preterm infants at 3 months corrected GA was 17.2±5.2 and 38.4±9.6 seconds respectively, which were significantly longer than in age-matched term infants (13.1± 2.7 and 28.9±5.0 seconds respectively) (P<0.05). The maximum response value of hemoglobin, oxyhemoglobin and regional oxygen saturation of the preterm infants at 3 months corrected GA was (1.2±0.5)%, (1.5±0.6)%, and (1.3±0.4) % respectively , which were significantly lower than that of the term infants [(2.3±0.3)%, (2.8±0.3)%and (2.4±0.5)% respectively] (P<0.05). Cerebral oxygenation responses to light stimulation in preterm infants examined at 6 months corrected GA were not significantly different from age-matched term infants. CONCLUSIONS: Cerebral oxygenation responses to light stimulation in infants born preterm at 3 months corrected GA are not as good as age-matched term infants, but were close to the level of age-matched term infants at 6 months corrected GA. This suggests that the early cognitive ability of preterm infants before 3 months corrected GA might fall behind age-matched term infants.