The study outlines the evaluation of an intellectual disability screening tool, the Child and Adolescent Intellectual Disability Screening Questionnaire (CAIDS-Q), with two age groups. A number of aspects of the reliability and validity of the CAIDS-Q were assessed for these two groups, including inter-rater reliability, convergent and discriminative validity. For both age groups, a significant positive relationship was found between full scale IQ and CAIDS-Q score, indicating convergent validity. Significant differences were found in the CAIDS-Q scores between those with and without an intellectual disability, with the former group scoring significantly lower. The sensitivity and specificity of the CAIDS-Q were above 96.7% and 85.5% respectively for the younger group and 90.9% and 94.9% respectively for the older group. Limitations and implications of the study are discussed.