Bronchopulmonary dysplasia (BPD), also known as chronic lung disease, is one of the most challenging complications in premature newborn infants. Selenium plays a role in antioxidant system by protecting cell membranes and neutralizing the deleterious effects of free radicals. The aim of this study was to determine the relationship between selenium concentration and incidence of bronchopulmonary dysplasia using a validated analytical method. Umbilical cord blood and blood samples 30 days after the birth were collected from 38 preterm newborn infants with gestation age of 32 weeks or less, and the separated serums were kept at -70°C until analysis time. Selenium concentration of serum was determined using an atomic absorption spectrophotometer. The method was validated on the basis of standard validation techniques. The analytical method was linear in the range of 1 to 500 μg/L with the limit of detection of 0.4 μg/L. Samples were collected from 38 infants whose gestation age was 32 weeks or less. The blood samples were collected from the umbilical cord blood at birth in 19 cases. In 25 cases, blood samples were collected 1 month after birth. Of the 15 patients diagnosed with BPD, 10 were boys (p = 0.02). The mean serum selenium concentration was not different at birth between patients with and without BPD, but it was significantly lower at 30 days after birth in patients with BPD (38.5 ± 14.1vs. 45.4 ± 18.7 μg/L, p = 0.02). Preterm newborn infants with BPD had lower serum selenium concentrations 1 month after birth.