Background and Objective: Inadequate vitamin D (insufficiency and deficiency) has been reported as one of the most important factors that might contribute to the increased occurrence of pediatric LRTI. This study was carried out to find the rate of vitamin D deficiency in children with acute lower respiratory infections. Materials and Methods: This case- control study was implemented on 2 to 60- month- old children diagnosed with LRI (Lower Respiratory Infection) or without LRI admitted to the pediatric ward of Mousavi Hospital in Zanjan. Both groups were similar in age and gender. Serum 25(OH) D levels were determined by direct enzyme-linked immunosorbent assay. Data were analyzed with version 16 of SPSS. Results: The mean vitamin D level for the entire LRI group was79/87 mmol/l and 67/35mmol/l for the control group. There was not any significant difference between the two groups. 12 patients had vitamin D deficiency. 36 had insufficient and 34 had sufficient vitamin D levels. Regarding these findings, there was not any significant difference between the case and control groups too. Conclusion: In this study no relationship was observed between vitamin D level and LRI in case and control groups despite high levels of inadequate vitamin D (insufficiency and deficiency) in both groups.