Non-adherence to medication is a chronic problem that impacts on healthcare professionals and patients alike. In psoriasis, a condition that presents patients with frequent and disabling physical, psychological and social effects, studies consistently suggest that up to 40% of patients do not use their medication as directed. Thus it is probable that poor adherence contaminates the clinical picture of response effectiveness in everyday practice. This educational paper reviews research that investigates adherence to medication in patients with psoriasis. It provides an overview of contributing factors and mediating variables. It is proposed that three specific facets appear to optimize patient adherence: an effective doctor-patient relationship; optimism with the treatment prescribed; and a limited 'nuisance' value of treatment in terms of side-effects and hassle of use. Various strategies to address adherence are suggested and it is argued that in order to enhance our understanding of adherence in patients with psoriasis, there needs to be an increasing focus on patients' beliefs about their condition and its management.