The article discusses the role of vitamin D in the development of skin pathology - in particular, psoriasis and acne. In some publications the results of vitamin D sufficiency in patients with these diseases are cited, but there is still insufficient information to draw definitive conclusions about the role of vitamin D in their development. The aim of the study was to assess the role of vitamin D in psoriasis and acne development. The case-control study involved 66 people, including 20 patients with psoriasis (group 1), 20 with acne (group 2) and 26 healthy individuals (control group). All participants in the study were determined the level of plasma vitamin 25 (OH)D; in patients with psoriasis PASI index to determine the severity of the disease was calculated. Vitamin 25(OH)D deficiency was detected in a significant majority of patients with skin diseases, and its average plasma level in each group was significantly lower than in the control group. There was a correlation between vitamin 25(OH)D deficiency and psoriasis severity. In patients with psoriasis and acne, vitamin D preparations should be included in the treatment complex to increase the effectiveness of therapy.