To assess the psychometric properties of 4-item questionnaire about sleep habits and time in South American children (3-10 years) and adolescents (11-18 years).We evaluated 459 participants from seven South American cities. Two items from week and weekend days wake up time and bedtime were asked twice, with a 2-week interval. We calculated time spent in bed (subtracting wake up time from bedtime). Participants also answered the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) sleep time questionnaire.The questionnaire showed acceptable temporal stability in children and adolescents on total days (rho≥0.30; p<0.05). For total days, the questionnaire presented acceptable convergent validity only in children (rho from 0.48 to 0.62; p≤0.01) compared with the HELENA questionnaire.The 4-item questionnaire is a reliable and valid tool for children; however, its validity is not consistent in adolescents for sleep habits and time.