This study compared clinical outcomes among adult, elderly and very elderly patients admitted to Intensive Care Units (ICUs) located in São Paulo, Brazil. This retrospective, longitudinal and comparative study included 279 adult (≥ 18 and <60 years), 216 elderly (≥ 60 and <80 years) and 105 very elderly (≥ 80 years) patients. Adult patients differed from other groups regarding the unit to which they were referred and severity, according to the Simplified Acute Physiology Score II. Adults were most frequently sent to hospitalization wards; elderly and very elderly patients who survived hospitalization in critical units showed sharper improvement before discharge. There were differences in relation to mortality between adult and elderly patients, with a higher rate in the elderly group; however, the mortality rate of very elderly and adult patients was similar. In general, the results indicated that older age was not associated with undesirable outcomes in ICUs.