Certain diseases and clinical conditions can become serious public health issues. This is particularly true in neurology where chronic headache illness is a burden borne by a great extent of the population. Assertively diagnosing headaches requires the patient to fill out printed forms and collect daily information that may help identify all possible causes. Nevertheless, these printed forms can also become an obstacle to the patients' treatment. This article presents MobiDiagnosis, a mobile system intended to characterize headaches that allows for storing and on-line analysis of the symptoms related information.