Psoriasis is a chronic disease, characterized by systemic inflammation with skin, joint and metabolic involvement. The most common tools to evaluate the severity of each disease is respectively the Psoriasis Area Severity Index (PASI) and the Disease Activity Index for Psoriatic Arthritis (DAPSA). The association between psoriasis and obesity and the role of visceral fat in producing an inflammatory state have been demonstrated. The Mediterranean Diet (MD) has been recommended as a model of healthy diet on the basis of scientific evidence and considered as an adjuvant therapy for all patients affected by chronic inflammatory diseases. Our study evaluated the association between adherence to MD (assessed with the Predimed questionnaire) and psoriatic disease severity. 80 patients (40 with psoriasis and 40 with psoriatic arthritis) were evaluated for disease severity (PASI, DAPSA) and were assessed for Metabolic Syndrome according to the International Diabetes Federation (IDF) definition. To evaluate adherence to the MD, each patient was administered the Predimed questionnaire which includes 14 questions. Our study shows a correlation between low adherence to MD and a high expression of psoriasis, considering cutaneous, joint symptoms and the metabolic profile.