Objectives: The purposes of the study were to assess complications and evaluate behavioral changes after dental treatment under general anesthesia in children. Methods: Complete records of 90 patients (54 male and 36 female) with the mean age of 4 years and 6 months (range 22 to 203 months) who underwent dental treatment under general anesthesia in Pediatric Dental Clinic, Mahidol University were reviewed for intraoperative adverse events and post-operative complications. Behaviors of patients were rated according to Frankl behavior rating scores before and after the dental treatment. Changes of behavior were analyzed using Wilcoxon Signed Ranks Test. Results: The patients were classified as ASA I (38.9%) and ASA II (61.1%) and 81% of the patients were rated as definitely negative. Of 55 patients in ASA II, 80% of patients were diagnosed as developmental behavior and emotional problems. No intraoperative complications were found. The common post-operative complications were fever (26.1%), nausea and vomiting (24.6%) and lip swelling (13%). None of the patients were retreated under general anesthesia. Patients' behavior were not different from their baselines at 6-month-recall but were significantly improved after 1 year (p<0.05). Conclusion: Only minor complications occurred following dental procedures under general anesthesia in ASA I and ASA II pediatric patients. Improved behavior of patients could be seen at 1 year after treatment.