BACKGROUND Childhood cancer, as one of the life threatening and most serious health problems, considerably influences the cognitive and social functions of children with cancer and their families; however, surprisingly enough, these children are quite compatible with their peers and even function better emotionally compared with normal children. This matter still remains to be a mystery. METHODS In this study, the ability of ignoring negative stimuli as a technique of emotion regulation was investigated in children with cancer. For this purpose, 78 children (33 girls and 45 boys aged 3 to 12 years) with pediatric acute lymphoblastic leukemia (ALL), and 89 healthy children (52 girls and 37 boys aged3 to 12 years) participated in this study. At the first stage, a number of positive,negative and neutral pictures were displayed to children. At the second stage, they were asked to identify the pictures from among a collection. RESULTS Data analysis by MANOVA indicated that children with cancer, compared with healthy children, could recognize more positive images than negative ones. Furthermore, it was found that age, sex, duration of hospital stay, duration of disease and financial situation had an effect on the difference between the two groups. CONCLUSIONS Positive bias memory can explain low depression and lack of symptoms of post traumatic stress disorder in children with ALL. Attention shifting is multifactorial phenomenon and neurologic factors and family support play important role in this happening.