The study was carried out to trace clinical laboratory parallels between levels of vitamin D under diseases of small intestine in children. The examined sampling included 160 children aged from 6 months to 18 years with diseases of small intestine. The patients were separated to three groups: 60 children with celiac disease aged from 3-16 years; 60 children with chronic post-infectious enterocolitis aged from 2 to 12 years; 40 children with allergic enterocolitis aged from 6 months to 4 years. The control group consisted of 31 children, including 15 children aged from 6 months to 4 years and 16 children aged from 5 to 18 years. The standard clinical, para-clinical and instrumental techniques of investigation were applied to every nosology. To analyze status of vitamin В the levels of calcidiol and parathormone were determined. In the process of tracing clinical laboratory parallels between levels of vitamin D under diseases of small intestine in children high percentage of decreasing of vitamin D (96.9%) was detected, and at that in 100% under celiac disease and chronic post-infectious enterocolitis. The feedback was established between levels of vitamin D and levels of calcidiol and parathormone and also activity of alkaline phosphatase in all groups of patients though more evident in patients with celiac disease and chronic post-infectious enterocolitis. The low values of level of vitamin D were detected in all children with celiac disease and chronic post-infectious enterocolitis whereas only in 87% under allergic enterocolitis. The decreasing of level of vitamin D was accompanied by increasing of content of calcidiol and parathormone and activity of alkaline phosphatase at that the most high numbers are observed in patients with celiac disease and then chronic post-infectious enterocolitis and allergic enterocolitis.