Purpose: The purpose of this paper is to explore Finnish adolescents' subjective health literacy (HL) in association to school achievement, learning difficulties, educational aspirations, and family affluence. Design/methodology/approach: Nationally representative data were collected in Finland as a part of the international Health Behaviour in School-aged Children study. The respondents consisted in total of 3,833 adolescents (7th and 9th graders) from 359 schools. The Health Literacy for School-aged Children instrument was applied to measure adolescents' subjective HL, while the Family Affluence Scale was used to measure adolescents' socioeconomic status. Information was gathered on school achievement, learning difficulties, and educational aspirations. Findings: Approximately one-third of the adolescents manifested a high level of HL, around 60 per cent had a moderate level of HL, and about one-tenth had low HL. The HL level was lower for boys than for girls, and lower for 7th graders than for 9th graders. In the total sample, the strongest explanatory variables for HL were school achievement in the first language, and educational aspirations. Originality/value: This study provides the first nationally representative examination of adolescents' subjective HL levels, and how these vary across age and gender groups. In drawing conclusions and presenting suggestions for HL interventions, it is important to verify the nature of the HL examined in any given study, and how it was researched.