Poor diet quality is a major modifiable risk factor for non-communicable diseases, which are a leading cause of morbidity and mortality globally. Plant-based diets are a growing area of interest for their potential health and environmental sustainability benefits, yet their nutritional quality can vary substantially depending on the foods consumed, highlighting the importance of understanding factors associated with healthful and unhealthful plant-based dietary patterns (1). Late adolescence is an important period for establishing dietary patterns that may persist into adulthood (2), yet limited research has examined the sociodemographic factors that influence plant-based diet quality during this life stage. This study aimed to investigate the sociodemographic correlates of plant-based diet quality among Australian adolescents at 17 years of age. This cross-sectional analysis used data from the Gen2-17 follow-up of the Raine Study, a longitudinal cohort study of Australian participants. A total of 351 participants were included in the analysis. Dietary intake was assessed using a validated CSIRO food frequency questionnaire. Plant-based diet quality was assessed using established indices: the overall Plant-based Diet Index (PDI), healthful Plant-based Diet Index (hPDI) and unhealthful Plant-based Diet Index (uPDI) (3). Hierarchical multiple linear regression was applied to examine this relationship, investigating parental education, household income, sex, adolescents' physical activity and smoking status. Analyses were adjusted for total energy intake (kJ) and parental ethnicity. Overall PDI was associated with higher education (p = 0.04) and being female (p < 0.001), higher hPDI scores were associated with being female (p < 0.001) and non-smoking (p = 0.007), and uPDI scores were associated with lower education (p = 0.039), being male (p = 0.001) and being a current smoker (p = 0.044). Physical activity and household income were not associated with plant-based diet quality (p > 0.05). In summary, adolescents who were female, had higher parental education, or were non-smokers had more favorable plant-based dietary patterns, whereas male adolescents, those with lower parental education and current smokers had less healthful patterns. These findings highlight sociodemographic differences in plant-based diet quality during late adolescence and may help identify groups who could benefit from targeted nutrition strategies and inform public health policy. Further longitudinal research using contemporary dietary data is needed to investigate how these patterns develop and change across adolescence and into adulthood.