Demodex mites are ectoparasites often found in the skin thought to be associated with the development of some skin diseases. Demodex positivity may be affected by several factors. In order to determine the relationship between Demodex infestation and rosacea disease (RD), Behcet's disease (BD) and various individual parameters such as gender, personal hygiene and skin type. A total of 238 individuals (61 with RD, 46 with BD, and 131 healthy subjects) were investigated for the presence of Demodex folliculorum and D. brevis using the standardized skin surface biopsy technique and a questionnaire. The incidence of Demodex mites in RD patients was significantly higher when compared to the control group (p=0.010 and p=0.001, respectively). However, there was no difference between those with BD and the control group. There was a significant difference between ages of groups, skin types, use of moisturizer, and itching, without taking into account the presence of Demodex among the disease groups (p<0.05). On the other hand, there was no significant difference between disease groups in terms of data of gender, skin care, epilation, and face washing. Our study reveals that the positivity rates of Demodex mites in rosacea patients were significantly higher. Mean ages of groups, skin types, use of moisturizer, and the presence of itching of the ear and face may be associated with higher density of Demodex mites.