BACKGROUND: This prospective, double-blind randomized study was performed to evaluate the analgesic effect of lesser palatine nerve block for postoperative pain control after a pediatric tonsillectomy, and to compare the analgesic effects of pre-emptive versus postoperative blocks. METHODS: Forty-eight ASA class 1 children, scheduled for an elective tonsillectomy were randomized into three groups. Patients received lesser palatine nerve blocks, using divided doses of 0.05 ml/kg of 0.2% ropivacaine, 5 min prior to the beginning of tonsillectomy (Pre-block group) or immediately after surgery (Post-block group). Patients allocated into the Control group did not receive any nerve block. Postoperative pain was measured immediately after surgery, 3, 6, 12 and 24 hours following operation using a 0 to 4 points pain scale, based on a facial expression of pain scale ruler. Side effects and the number of analgesic injections were observed for 24 hours postoperatively. RESULTS: No significant differences in the pain scores were observed immediately after surgery and at 3, 6, 12 and 24 hours after operation in the three groups (P > 0.05). The number of analgesic injections was similar in the groups. CONCLUSIONS: The results of this study reveal that the lesser palatine nerve block was not effective for postoperative pain control following pediatric tonsillectomy, and that the pre-emptive block offered no pain control benefit over the postoperative block. Therefore, we do not recommend lesser palatine nerve blocks for the management of postoperative pain after pediatric tonsillectomy.