Excessive intakes of added and free sugars are associated with several adverse health effects. However, due to an absence of objective or standardised methods to measure intake, there is limited knowledge about consumption, including in Swedish adolescents. Adolescence is a critical period for establishing healthy dietary habits, as food patterns formed during these years often persist into adulthood, influencing longterm health. Dietary habits of Swedish adolescents overall fail to meet dietary guidelines. The adolescent diet is generally low in vegetables and fruit, dietary fibre and wholegrains, alongside high in saturated fats, salt, and sugars. Despite these concerns, intake levels of added or free sugars have not previously been quantified in Swedish adolescents. The overarching aim of this doctoral thesis is to examine dietary intake in Swedish adolescents, emphasising added and free sugars intake.