The purpose of this study was to examine the relationship between the intelligence quotient score of the Wechsler Intelligence Scale for Children-Third Edition; Thai version (WISC-III-Thai version) and the Leiter International Performance Scale-Revised (LeiterR) and to compare the difference of the scores in both tests. Further comparison was made between the full scale IQ (FSIQ) and the verbal component subtests; Vocabulary and Digit Span. The subjects were 30 children who had been diagnosed with learning disabilities by a physician according to DSM-IV diagnostic criteria. The participants received service from February to May 2010 at HRH Princess Maha Chakri Sirindhorn Medical Center. A sample of children with learning disabilities as determined by the WISC-III-Thai version and Leiter-R. The statistics used in this study are the percentage, average, standard deviation, Pearson Product Moment Correlation Coefficients, and Pair Sample t-test. The results of this study were concluded as follows: (1) There was a statistically significant FSIQ score relationship in both tests at 0.01 (r=.527 and .502 respectively). (2) There was no significant difference in the mean score between both tests. (3) There was no significant difference in mean FSIQ score between vocabulary and digit span subtests in the verbal component of WISC-III-Thai version. (4) Corresponding percentages between the FSIQ score from the vocabulary and digit span subtests of WISC-III Thai version compared with Leiter-R test was 93.33 % and 86.67%, respectively.  This current study showed that the Leiter-R test is a valid clinical tool that can be used to evaluate the level of intelligence, and diagnostically screen children for learning disabilities. This can lead to appropriate recommendations for interventions of modification or accommodation in their educational plan as well as therapeutic remediation programs as treatment modalities.