Prior to surgery, 47 children (ages 8 to 17) with borderline to profound cognitive impairment were administered tasks to evaluate their understanding of the concepts of magnitude and ordinal position and their abilities to use a 0 to 5 numerical scale to rate pain levels in schematic faces. Of the 111 children (ages 4 to 14) without cognitive impairment, were administered the same tasks. Nurses conducting preoperative evaluations predicted whether children would understand the numerical scale. Fifty percent (n = 3) of children with borderline and 35% (n = 7) of children with mild cognitive impairment (and all children 8 years and older nonimpaired) correctly used the scale. Half of the children with cognitive impairment demonstrated skills (magnitude and ordinal position) that may allow them to use simpler pain rating methods. Nurses overestimated the abilities of cognitively impaired children (and younger children without cognitive impairment) to use the rating scale.