Purpose The purpose of this study was to investigate the effects of topiramate on language and problem solving ability in newly diagnosed pediatric patients with epilepsy. Patients and Methods Forty newly diagnosed pediatric epileptic patients (aged 7―12 years) were investigated in this study from May 2006 to February 2009. Topiramate was administered 1mg/kg/day for the first one or two week, followed by slow increase of dose every 2week intervals until a maintenance dose of 5mg/kg/day or 200mg/day reached. First test data were collected right before the topiramate monotherapy started and the treatment remained as monotherapy until the second tests were performed, patients themselves were the control group. We also compared the data from patients and similar aged healthy volunteers. We performed a standardized full articulation test and Peabody picture vocabulary test―revised. To assess the language characteristics of the patients, Test of Problem Solving (TOPS), Mean Length of Utterance in words, comparison of Precise Articulation, Computerized Speech Lab (KAY Elemetrics, 2004, USA) were used. Results First, TOPS showed that the abilities of problem solving were worsen after initiation of topiramate in preschool and school aged patients. All parameters: Causal reason (11.1± 4.7 vs 9.6 ± 3.5), solution ratiocination (10.9 ± 3.9 vs 9.1 ± 2.3), beginning guess (7.1 ± 2.9 vs 6.6 ± 2.5) were significantly reduced after initiation of topiramate ( P0.05). Second. Patients with topiramate showed shorten the mean length of utterance in words (5.3 ± 1.0 vs 4.8 ± 0.7, P0.05), answers were ambiguous during the test, and they also showed that the difficulty to select the appropriate word, took more time to answers, and used the wrong grammar. Third, no statistically significant change in receptive language of kindergarten and elementary school students were seen (6y 3m ± 1y 2m vs 7.0y ± 1y 1m, P＞0.05). There were no significant change in vocabulary, precise articulation of kindergarten and elementary school students even after taking TPM (96.1% vs 96.4%, P＞0.05). Conclusions Our data suggests that topiramate could be negative effects on the abilities of problem solving and language abilities. We strongly recommend that language tests should be performed during the treatment with topiramate in children.