Studies focusing on young children's self-reported health-related quality of life (HRQoL) are scarce. More research is needed on the reliability and validity of the methods as well as how self-reported HRQoL in early childhood is linked to other well-being factors. Using the Kiddy-KINDL questionnaire in interviews with 245 3- to 6-year-old children this study investigated how children view their quality of life in Swedish speaking early childhood education and care in Finland, how reliably it can be assessed, and how it relates to age, gender, parent-reported socioeconomic background, and teacher-reported psychological well-being. The results showed that only the social-emotional scale consisting of eight items was a reliable index of HRQoL. The correlation over time in the 12-week follow-up was significant, but small, which may reflect children's here and now thinking. Children's poorer self-reported social-emotional well-being was associated with externalizing problems as reported by the teachers. Older children and children from highly educated families reported better social-emotional well-being.