The study analysed two key questions: (i) the prevalence of informal caregiving in medical and surgical wards of a high specialization hospital; (ii) the reasonable cost for the structure that would have to pay to replace informal caregiving? The study was conducted in June 2006 as a prevalence survey, using a questionnaire administered to informal caregivers and nurses working in medical and surgical wards of a high specialization hospital by ad hoc trained personnel. Questionnaire consisted in three sections: the first focused on patient's characteristics, the second on caregivers and the third on nurses' perception on caregiving phenomenon. One hundred and twenty-four eligible caregivers were identified. During the study patients admitted to hospital medical and surgery wards were 520. Among these 16.5% (86/520) was assisted by one or more caregivers. Caregivers' response rate was 69.4% (86/124), corresponding to 66 patients. This study yielded an average of 455.9 minutes per day (SD = 370.2; range = 120-1440) or 52.9 hours per week. Caregiver's presence was recognized in 88.9% (56/63) of patients. Despite the societal perspective, the costs and effects of informal caregiving to the informal caregiver are often ignored in economic evaluation. The costs of informal care are an important extent related to time inputs by relatives and friends of the care recipients. Our approach has been to monetize the informal activity care contribution of family members and/or caregivers.