Recently, it has emerged a strong association between increased adiposity, obesity, and psoriasis. Body Mass Index (BMI) is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults. Psoriasis has also been associated with systemic obesity-related disorders including type 2 diabetes, hypertension, ischemic heart disease, and combined hyperlipidemia, as a part of metabolic syndrome. Not only the obesity may be associated with higher psoriasis incidence and activity, and prevalence of obesity-related syndromes, but it may also influence the therapeutic approach to disease and the clinical response to systemic treatment. Consequently, the approach of the experienced dermatologist will take into account all the aspects of the patient clinical conditions including the analysis of BMI for the choice of the best suitable therapy.