Overall, the reviewed literature indicates self-reports of pain are sensitive in capturing qualities of the pain experience, although they are subject to personal response biases, reflect the person’s appraisal of the consequences of the pain report and require certain cognitive skills. For example, children’s self-reports of pain intensity are a valuable source of information, but their interpretation must be considered together with observation of behaviour, reports by parents, clinical data and information on the child’s social environment, especially for pre-school aged children. Estimates of pain intensity based on these other sources may not always correlate highly with children’s self-report of pain, and may reflect different perspectives of the pain experience. An NRS with numbers from 0 to 10 (“no pain” to “worst pain”) is more practical than a VAS, easier to understand for most people, and does not need clear vision, dexterity, paper, and pen. The NRS functions best for the patient’s subjective feeling of the intensity of pain at that moment. They may be used for worst, least, or average pain over the last 24 hours, or during the last week. There are limitations with this, as memory of pain is not accurate and often distorted by changing context factors.