To examine the possible associations between Demodex folliculorum and a number of skin diseases.Standardized skin surface biopsy samples were obtained from the cheeks of 144 patients with histopathologically proven basal cell carcinoma (BCC, n = 27), squamous cell carcinoma (SCC, n = 28), melanoma (n = 23), discoid lupus erythematosus (DLE, n = 32), and rosacea (n = 34). Thirty-four sex- and age-matched healthy volunteers served as controls. Mite density (per cm2) and infestation (density ≥ 5) were compared between the controls and patients.Mite infestation rates (%) did not differ significantly between the controls (20.6) and patients with BCC (22.2, p = 0.88), SCC (17.9, p = 0.79), melanoma (4.3, p = 0.08), and DLE (21.9, p = 0.90). Compared with the controls, the mite infestation rate was significantly higher in patients with rosacea (47.1, p = 0.02, odds ratio: 3.43, 95% confidence interval: 1.18-9.99). The mean mite density did not differ significantly between the controls (4.11 ± 2.17) and patients with BCC (5.34 ± 2.35, p = 0.75), SCC (3.57 ± 2.01, p = 0.38), and DLE (3.56 ± 1.34, p = 0.83), whereas it was significantly higher in patients with rosacea (8.78 ± 3.58, p = 0.02) and lower in patients with melanoma (1.89 ± 0.69, p = 0.02).D. folliculorum may be associated with rosacea and melanoma but not with BCC, SCC, or DLE.