OBJECTIVE The aim of this paper was to determine whether the use of midazolam is a better technique than the use of diazepam, in relation with the definition of conscious sedation in dentistry. METHODS Eighty-eight patients undergoing oral surgery were divided into 2 groups in which the sedation was randomly achieved with equipotent cumulative doses of diazepam and midazolam, up to a maximum dose of 8 and 4 mg respectively. Patient's tranquillity was assessed after every dose, using a visual analogue score to ten points and the sedation was evaluated as mild, moderate or deep. Blood pressure, heart rate and SpO2 were also recorded. Psychomotor conditions, by Newman test, and the incidence of amnesia and the patient's satisfaction, by telephone interview, were both evaluated. RESULTS The number of patients who reached maximum subjective tranquillity was greater already after the third dose of diazepam. The average scores of tranquillity were higher after diazepam. Patients treated with diazepam experienced a higher incidence of mild sedation, patients treated with midazolam a higher incidence of moderate and deep sedation. In patients treated with midazolam blood pressure, heart rate and SpO2 were lower. Postoperative recovery was similar in the 2 groups. After midazolam patients experienced greater amnesia for local anesthesia and drowsiness. Satisfaction was high with both treatments. CONCLUSIONS The study shows that sedation with diazepam is more in line with the definition of conscious sedation in dentistry. Diazepam guarantees the persistence of consciousness and maximum subjective tranquillity levels. The recovery and satisfaction were comparable in the 2 groups.