Introduction: Psoriasis is a common inflammatory skin disorder with humeral and cellular immune system involvement. On the other hands، Vitamin D has important immunomodulatory effects and its relations with many autoimmune diseases were shown. The relation between Serum Vit D Level and Psoriasis disease remained controversial issue that this study was done to show this relationship.

Methods and Materials: In this comparative cross sectional study، 30 psoriatic patients who attended to Razi dermatology clinic in Rasht، by sequential sampling underwent study as case group. 30 healthy people from hospital at the same age، gender and skin-colored also were selected as control group. Inclusion criteria were patients and people without Ca or Vit D supplements usage or underground diseases in relation to hypovitaminosis D. Demographical data were gathered by interviewing and then blood samples from all participants were sent for analysis of serum Ca، P، Vit D and parathormone level. Data analysis was done by SPSS ver. 18 using T-test and Chi ² test.

Result: Mean and SD serum level of Vit D in case and control groups were 25.8± 12.6 ng/ mL and  23.7± 8.9 ng/ mL، respectively (ρ>0.05). Out of all، 24 participants (40%) suffered from Vit D Deficiency and 20 people (33.3%) from Vit D insufficiency ، only 26.7% study subjects had acceptable serum Vit D level. There were not any significant difference between Vit D deficiency rates and other measured biochemical indices in two groups (36.7% vs. 43.3%).

Conclusion: This study showed high level of Vit D deficiency in both psoriatic and normal people that must be notice.