OBJECTIVES: To assess WTP of patients and accompanying family members or carers for a brand name drug (BD) as compared to a GD for treating an acute and a chronic condition. METHODS: 25 patients and 25 accompanying family members or carers were consecutively selected and interviewed while visiting 6 commercial pharmacies located in different regions of São Paulo city. Also another 25 patients and 25 accompanying family members or carers were consecutively selected and interviewed while waiting for their regular outpatient visits at the university outpatient clinic. A questionnaire with 2 hypothetical scenarios describing an acute condition (acute tonsillitis in an 8 year old child) and a chronic condition (an adult with diabetes mellitus type 2) was developed. WTP for a BD as compared with a GD was assessed in both scenarios using the payment scale and the open-ended formats. The study was approved by the local ethical committee. RESULTS: Respondents were predominantly women (57%) and the mean age was 54 y.o. A family income of less than R$ 1.356,00 was reported by 16%. For the total study sample, the maximum WTP for a BD (over and above the mean retail price of a GD) for the acute and chronic case scenarios were on average R$ 27,54 and R$ 21,04 when measured by the payment scale and R$ 36,54 and R$ 24,77 when measured by the open-ended question, respectively. These values are 36% to 65% above the mean retail prices of the corresponding GD. CONCLUSIONS: Patients and accompanying persons were willing to pay considerably more for the BD when compared to GD. This may be driven by the perception of higher perceived effectiveness and safety of BD.