OBJECTIVES: The assessment of a patient’s disease severity is an essential component in the formulation of treatment strategies. This study wants to compare the dermatological disease severity assessment by patients and by physicians, and to describe the possible discrepancies between them.METHODS: For each patient, we obtained the Physician Global Assessment (PhGA) and the Patient Global Assessment (PtGA).  Data were completed for 2.578 patients.  Sixty-one physicians participated in the study. We calculated the agreement  between PtGA and PhGA  scores using the weighted kappa statistics; a multinomial logistic regression was performed to assess the risk of  disagreement considering both patient and  physician variables. RESULTS: Differences in the percentages of  severity level, identified by patients and by physicians, were always statistically significant (p<0.05).  Overall, the weighted Cohen’s kappa  was in the range of 0.09 - 0.34, depending on the diseases.  Gender differences between patients and physicians did not influence the agreement. In the multinomial model female patients (OR=1.38; 95%CI, 1.07-1.77), patients with higher educational levels (OR=2.71; 95%CI, 2.12-3.46), and patients with impaired quality of life (OR=1.56; 95%CI 1.23-1.97) had a higher risk to be underestimated for their disease severity by physicians, independently by physician gender and experience. CONCLUSIONS:    Combining the subjective report with the objective severity assessment of the lesions, dermatologists may reach a better determination of how severity of disease is perceived by their patients and how they feel about the effectiveness of treatment. PtGA and PhGA might be considered in routine clinical assessments and not only for research activities.