A review of clinical records was conducted for children with developmental, emotional, and behavioral difficulties who were assessed with both the Wechsler preschool and primary scale of intelligence-third edition (WPPSI-III[superscript CDN]; Wechsler, 2004) and the Leiter international performance scale--revised (Leiter-R; Roid & Miller, 1997) within the same psychological evaluation. Forty children, ages 3-7, were included in this study. Pearson correlations showed that the IQ scores of the two instruments are strongly related (r > 0.70; p < 0.001). However, paired t-tests showed that overall Leiter-R scores (M = 99.03) were significantly higher than WPPSI-III[superscript CDN] scores (PIQ; M = 82.28, FSIQ; M = 75.24) (p < 0.001). The discrepancies between the instrument's scores were clinically important as the use of only one of the two instruments could result in misclassification of child intellectual ability. These results should prompt professionals working with this clinical population to be cautious when using results from a single instrument in a child's intellectual evaluation.