PURPOSE: We compared neurodevelopmental outcomes according to prenatal and postnatal growth patterns in preterm infants and evaluated the proper catch-up growth timing and risk factors that affect poor neurodevelopmental outcomes. METHODS: We retrospectively reviewed the electronic medical records of preterm infants born at <32 weeks of gestational age or with <1,500 g of birth weight, who were tested with the Bayley scales of infant and toddler development, third edition (Bayley-III), at 8 and/or 18 months of corrected age in the outpatient clinic. Study populations were divided into four groups according to catch-up growth patterns, which were evaluated about <10th or ≥10th percentile at birth and at 8 or 18 months. RESULTS: In this study, 107 preterm infants were enrolled and 149 results of Bayley-III were analyzed. Infants whose lengths were within <10th percentile at birth had lower cognitive score than those whose lengths were ≥10th percentile at birth (P=0.007). The catch-up growth of length affected cognitive score (P<0.001), and the catch-up growth of head circumference affected cognitive (P<0.001) and motor scores (P=0.024). The catch-up growth of head circumference by 8 months than that by 18 months was more correlated to cognitive (R2=0.300 vs. 0.266, respectively) and motor development (R2=0.257 vs. 0.210, respectively) at 18 months. CONCLUSION: Appropriate body length at birth in preterm infants was significantly associated with optimal cognitive development. Catch-up growth of body length was related to cognitive development, while catch-up growth of head circumference was related to both cognitive and motor development. Earlier catch-up growth of head circumference was more critical for neurodevelopment than weight and length.