Aims: To determine the prevalence of vitamin D deficiency in children (6 months - 5 years of age) with recurrent pulmonary-pulmonary infections, staying in an outpatient setting. Place and Duration: In the Pediatric Unit-II of Holy Family Hospital, Rawalpindi for one-year duration from November 2019 to November 2020. Methods: It was a descriptive study conducted on children aged 6 months to 5 years. 1000 children were enrolled in the study, and their data were recorded on a previously prepared proforma. Results: Of 1000 cases, 830 (83.0%) children were deficient in vitamin D3 (group I), 112 (11.2%) had vitamin D3 deficiency (group II), which is 94.2%, 57 (5.7 %) had the desired level (group III) and 1 (0.1%) had vitamin D intoxication (group IV). In this age group, more children were 1-3 years old. 236 (23.6%) were ranging from 1 to 2 years, 256 (25.6%) from 2 to 3 years. 602 (60.2%) were males and 398 (39.8%) females. Most of them had bronchiolitis 356 (35.6%), followed by pneumonia 320 (32.0%), otitis media 194 (19.4%), and acute tonsillitis 134 (13.4%). In group I (n = 830), bronchiolitis 352 (42.4%) and pneumonia 296 (35.6%) were more common, and less common was acute tonsillitis 72 (8.6%). In group II (n = 112) 52 (46.42%) had bronchiolitis, 32 (28.5%) had pneumonia, and less commonly had acute tonsillitis (8.9%). In group III (n = 57), the dominant diagnosis was tonsillitis [23 (40.35%)], followed by bronchiolitis [9 (15.7%)]. Conclusions: Children 6 months to 5 years of age with recurrent sino-pulmonary infections ie (bronchiolitis, pneumonia, otitis media and acute tonsillitis) tended to be deficient in serum vitamin D3. It is recommended that vitamin D3 levels be assessed in all children with recurrent respiratory infections. Key words: Vitamin D3 level, sino-pulmonary infections, pneumonia, bronchiolitis, otitis media, acute tonsillitis.