Objective: To determine the prevalence of seborrhoeic dermatitis (SD) and atopic dermatitis (AD) between the Demodex folliculorum (D. folliculorum) positive and D. folliculorum negative patients and to investigate any possible relationship between the D. folliculorum mites and the presence of SD and AD. Methods: In this cross sectional study, authors collected samples from the skin around the nasal tip of 180 randomized patients who reffered to Amir Al-Momenin Hospital dermatology clinic for skin erythema, scaling and pruritis, to examine the precence of demodicosis (D. folliculorum) infestation under optical microscope. Then authors assessed the prevalence of SD and AD between the D. folliculorum positive and D. folliculorum negative patients. Finally, data analysis using SPSS software and Chi-square test were performed. Results: Our study showed no significant association between the demodicosis (D. folliculorum) and SD (P=0.68) and AD (P=0.70) prevalence. Conclusions: According to the result of this study, the eradication of Demodex mites probably is not effective to reduces the prevalence of both dermatitis. However further investigation on a larger scale in a case-control study in this area is recommended.