The data about the prevalence of onychomycosis in patients with psoriasis is contradictory. In this study, we investigated the prevalence of onychomycosis and tinea pedis in patients with psoriasis compared to control group. A total of 60 patients with psoriasis (27 male, 33 female; mean age: 40.8 +/- 17.6 years) and 60 subjects without psoriasis (27 male, 33 female; mean age: 42.8 +/- 17.3 years) who were admitted to dermatology outpatient clinics of our hospital were included to the study. Scrapings from both normal and abnormal toenails as well as toewebs were examined using microscopy and fungal culture. Foot dermatomycosis was diagnosed in 6 (5 onychomycosis and 1 tinea pedis) patients with psoriasis (10%) and in 8 (5 onychomycosis and 3 tinea pedis) control subjects (13.3%) (p>0.05). The only dermatophyte fungi isolated in both patients with psoriasis and control group were Trichophyton rubrum (75%) and Trichophyton interdigitale (25%). Onychomycosis was more predominant in male psoriatic patients (p=0.01). Both distero-lateral subungual onychomycosis (DLSO) and total dystrophic onychomycosis were detected in patients with psoriasis, however, DLSO, was the only clinical type in the control group. Pitting is the most typical lesions in nails in patients with psoriasis (p=0.04). The use of common showers play a role in transmission of foot dermatomycosis (p=0.04). In this study, psoriasis was not found as a risk factor for onychomycosis. However, onychomycosis is a major problem in psoriatic nails, and mycological methods would be useful in differential diagnosis. Since dermatomycosis is still an important public health problem, it may be controlled by education of the patient about proper foot hygiene and avoiding walking barefooted in shower areas.