Pain management in ambulatory care regularly requires the prescription of opioids. These drugs allow adequate analgesia achievement in many patients, but inefficiency and/or intolerable side effects may limit their use. Factors related to physiological particularities, comorbidities and comedication, as well as difficulties related to drug intake and pain assessment, make children and the elderly more vulnerable to variability in opioid response and problems of safety and efficacy profile. The purpose of this article is to remain the specificities of these two populations and to propose recommendations for the good use of opioids for ambulatory care.