The Complete State Model of Mental Health was used to describe the prevalence of flourishing, languishing, struggling, and floundering in life in a sample of young South Australians (n = 3,913; 13–17 years, 52% female). Categorisation was based on the relative proportion of mental health and mental illness symptoms reported on standardised measures and the association of these categories to health-risk behaviour. Variability in categories and health-risk behaviour due to gender or region was investigated. Results indicated that a disturbingly small proportion of adolescents (<50%) were flourishing in life, that poorer states of mental health were associated with increased health-risk behaviour, and that the propensity to engage in health-risk behaviour did vary by gender and region. The current study extends the platform from which positively focused mental health strategies can be tailored and launched to meet the mental health needs of adolescents.