Background: Health behaviours do not occur in isolation. Rather they cluster together. It is important to examine patterns of health behaviours to inform a more holistic approach to health in both health promotion and illness prevention strategies. Examination of patterns is also important because of the increased risk of mortality, morbidity and synergistic effects of health behaviours. This study examines the clustering of health behaviours in a nationally representative sample of Irish adults and explores the association of these clusters with mental health, self-rated health and quality of life.Methods: TwoStep Cluster analysis using SPSS was carried out on the SLAN 2007 data (national Survey of Lifestyle, Attitudes and Nutrition, n = 10,364; response rate = 62%; food frequency n = 9,223; cluster analysis n = 7,350). Patterns of smoking, drinking alcohol, physical activity and diet were considered. Associations with positive and negative mental health, quality of life and self-rated health were assessed.Results: Six health behaviour clusters were identified: Former Smokers, 21.3% (n = 1,564), Temperate, 14.6% (n = 1,075), Physically Inactive, 17.8% (n = 1,310), Healthy Lifestyle, 9.3% (n = 681), Multiple Risk Factor, 17% (n = 1248), and Mixed Lifestyle, 20% (n = 1,472). Cluster profiles varied with men aged 18-29 years, in the lower social classes most likely to adopt unhealthy behaviour patterns. In contrast, women from the higher social classes and aged 65 years and over were most likely to be in the Healthy Lifestyle cluster. Having healthier patterns of behaviour was associated with positive lower levels of psychological distress and higher levels of energy vitality.Conclusion: The current study identifies discernible patterns of lifestyle behaviours in the Irish population which are similar to those of our European counterparts. Healthier clusters (Former Smokers, Temperate and Healthy Lifestyle) reported higher levels of energy vitality, lower levels of psychological distress, better self-rated health and better quality of life. In contrast, those in the Multiple Risk Factor cluster had the lowest levels of energy and vitality and the highest levels of psychological distress. Identification of these discernible patterns because of their relationship with mortality, morbidity and longevity is important for identifying national and international health behaviour patterns.