BACKGROUND AND OBJECTIVE: With the advancement of medical care procedures, survival rate of preterm neonates has increased remarkably. In Iran, few studies have assessed the extent and severity of developmental disorders in these infants. This study aimed to evaluate developmental disorders in premature neonates.METHODS: This cohort study was conducted on 270 premature infants born in Ghaem Hospital in Mashhad, Iran with mean birth weight of 1460±40 grams. Data on pregnancy, parturition and complications during hospitalization were recorded. Moreover, preterm neonates were evaluated in terms of developmental delay at 6, 12, 18 and 24 months of age based on the Ages and Stages questionnaire (ASQ).FINDINGS: In this study, symptoms of developmental delay were observed in 152 neonates (56%) at six months, 115 neonates (42.7%) at 12 months, 101 infants (37.5%) at 18 months, and 49 neonates (18%) at 24 months. In addition, abnormal development was detected in different areas, including communication (n=21, 7.8%), major movements (n=53, 19.6%), minor movements (n=74, 27.5%), social interactions (n=89, 33%), and problem solving (n=153, 57%). After a two-year follow-up, 27 infants (60%) had asphyxia, 29 (28%) had respiratory distress syndrome, and 20 infants (15%) had developmental disorders.CONCLUSION: According to the results of this study, about one-sixth of preterm neonates had developmental delay at two years of age. The highest rate of developmental disorders was observed in the area of problem solving, which should be taken into account in neonatal rehabilitation services. On the other hand, appropriate monitoring of neonatal asphyxia and jaundice is likely to reduce the risk of other complications during infancy.