BACKGROUNDVitamin D deficiency causes several health problems. We investigated the frequency of vitamin D deficiency and insufficiency and theimpact of seasonal variation on the 25-Hydroxyvitamin D [25(OH) D] levels of healthy children living in Cyprus.METHODSA total of 565 healthy children (aged, 0-18 y) under routine pediatric consultation who were followed in our Department of Pediatricsbetween February 2013 and September 2016 and who were screened for 25(OH) D level were included.RESULTSThis analysis demonstrated a frequency of 22.5% vitamin D deficiency and 29% insufficiency. 25(OH) D results had a positive correlationwith temperature (r=0.25, p=0.00) and a negative correlation with age (r=-0.43, p=0.00). 25(OH) D deficiency was more frequent in femalesthan in males (p=0.04). Deficiency was the most frequent during winter and spring and the least frequent during summer (p=0.00).Deficiency was the most frequent in December and April and the least frequent in June and July (p=0.00), and it was the least frequentin children in the age group of 0-12 month sand the most frequent in those in the age group of 169–216 months (p=0.00). Within this group,85 of children were evaluated for Ca, P, and alkaline phosphatase (ALP). 25(OH) D results did not have a correlation with Ca, P, and ALPvalues. When the vitamin D deficient and sufficiency groups were compared, Ca (p=0.01), P (p=0.03), and temperature (p=0.04) valueswere lower in the deficient group.CONCLUSIONVitamin D deficiency is an important health problem even in our country, which has sufficient sun exposure. Therefore, children shouldspend more time outdoors to adequately benefit from vitamin D synthesis from sunshine.