The numerous pain rating scales using faces depicting varying degrees of distress to elicit reports of pain from children fall into two categories; those with a neutral face as the 'no pain' anchor, and those with a smiling face as the 'no pain' anchor. This study examined the potentially biasing impact of these anchor types on children's self-reports of pain in response to a series of vignettes. Participants were 100 children stratified by age (5-6 years, 7-8 years, 9-12 years) and randomly assigned to one of three groups: (1) neutral scale/sensory instructions; (2) smiling scale/sensory instructions; (3) smiling scale/affective instructions. Children completed a faces scale, a VAS, and emotions ratings in response to four scenarios depicting: (1) no pain/negative emotions; (2) pain/negative emotions; (3) no pain/positive emotions: (4) pain/positive emotions. Results showed that children who used the smiling scale had significantly higher pain scores for no pain and pain/negative emotions vignettes and significantly lower faces scale scores for pain/positive vignettes than children who used the neutral faces scale. Instructions varying in focus on sensory or affective qualities of pain had no effect on children's pain ratings. Group differences in children's ratings with the VAS and emotions measure suggested that rating pain with a smiling faces scale may alter a child's concept of pain. Age differences indicated the younger children rated the negative emotion vignettes as more painful than the older children. These findings suggest that children's pain ratings vary depending on the types of faces scale used, and that faces scales with smiling anchors may confound affective states with pain ratings.