In children, assessment and measurement of pain is challenging. The difficulties of pain assessment in children can be explained by their constantly changing state of perception, interpretation and expression of pain related to age, developmental stage, previous pain experiences, and other modifying environmental factors. Unlike most adults, children (especially younger ones) lack the cognitive and behavioral competency both to understand questions concerning their pain and to describe their pain. Especially very young children don’t have pain experience and cooperation with adults is limited. Age, general health status and ability of self report are the factors that must be considered when selecting appropriate method of pain measurement and pain assessment must be repeated regularly. Although many different tools are used to measure and assess pain, no single one supplies enough information about pain and its different components to be used as the standard measure of pain in children.