In this study, the effects of eliciting positive and negative emotions on various cognitive functions of four- to five-year-old preschool children were examined. Emotions were elicited through presentations of "happy" and "sad" video clips, before the children performed the cognitive tasks. Behavioural (facial expressions) and physiological (heart rate variations) indices of emotions were used to measure the elicited emotions. The impact of emotions on analytical as well as global thinking was examined. Positive emotions were found to generate an overall improvement in children's cognitive functioning. This finding is inconsistent with findings reported in research conducted among adults, suggesting differential effects of emotions on cognitive performance of children and adults. It was also found that children's improved cognitive performance after eliciting positive emotions occurred predominantly on tasks related to subject areas they were familiar with. The findings are discussed within a developmental framework. (Contains 3 tables.)