OBJECTIVE Hydatid cyst still continues to be a public health problem. The basic treatment for the disease is surgery, but ultrasound-guided percutaneous drainage has become an important treatment alternative. Agents preferred for sedation during drainage performed under local anaesthesia must also preserve respiration and hemodynamic stability while providing adequate sedation. We compared the sedative properties of midazolam, which has a short duration of action, and a selective α2 adrenergic receptor agonist, dexmedetomidine, and the intraoperative complications. METHODS After approval by the clinical trials ethics committee, 40 patients with similar demographic data were randomized into two groups. All patients received 10 mg metoclopramide and 45.5 mg pheniramine before the procedure. Then, midazolam (0.07 mg kg(-1) IV bolus followed by 0.01 mg kg(-1) h(-1) infusion) was administered to Group 1, and dexmedetomidine (1 μg kg(-1) loading dose in 10 minutes, followed by 0.2 μg kg(-1) h(-1) continuous infusion) was administered to Group 2 for sedation. Just before the surgical procedure, all patients received IV propofol in a subhypnotic dose of 0.5 mg kg(-1); the dose was repeated if adequate sedation could not be achieved. Observer's assessment of alertness/sedation (OAA/S) scale and Bispectral index (BIS) were used to evaluate the sedation level during the procedure. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (RR), peripheral oxygen saturation (SpO2) and end-tidal carbon dioxide pressure (ETCO2) were monitored before and after induction and every 5 minutes thereafter. Propofol requirement was noted for each group. RESULTS Sedation in the dexmedetomidine group was as effective and adequate as that observed in the midazolam group. BIS values were significantly lower in the dexmedetomidine group, especially after 10 minutes and thereafter. RR, SpO2, and ETCO2 were similar in both groups, whereas clinically insignificant decreases in HR and MAP were observed in the dexmedetomidine group. Propofol requirements were similar in both groups. CONCLUSIONS We conclude that dexmedetomidine, providing adequate sedation without respiratory depression, can be considered as an appropriate agent for sedation in surgical procedures performed under local anaesthesia.