As reflected in numerous behavioural theories, knowledge and attitudes are key determinants of whether individuals engage in health-related behaviours. These factors are likely to be especially relevant where recommended behaviours require effort, are considered unappealing, and/or have strong competition. The aim of this study was to assess knowledge and attitudes relating to diet and physical activity among Australian teenagers to inform future interventions to improve health outcomes in this group. Of particular interest was whether similar knowledge and attitudinal outcomes were apparent between the domains of PA and nutrition. Eight focus groups were conducted with 72 teenagers (12-17 years of age) in Western Australia. The groups ran for an average of 80 minutes. The sessions were audio-recorded and the resulting transcriptions were imported into NVivo for analysis. Most of the participants could cite specific nutrition guidelines (e.g., consume 2 fruits and 5 vegetables per day), differentiate between healthy and unhealthy foods, and discuss at length why a healthy diet is important. By comparison, few could nominate the recommended level of PA for their age group (60 minutes/day) and they appeared much less certain about what kinds of exercise are recommended and why. It was generally considered easier to eat healthily than to engage in regular PA, largely because of the many other perceived demands on their time and the amount of sedentary time spent using various forms of media. In conclusion, while generally appreciative of the importance of PA, teenagers may lack the level of understanding needed to motivate engagement in recommended levels of activity. Specific suggestions for future interventions designed to cater for this population segment will be discussed. The study was funded by the WA Health Promotion Foundation (Healthway).