AbstractObjectiveTo investigate the relationships between weight reduction behaviour among non-overweight schoolchildren and dietary habits, perception of health, well-being and health complaints.DesignAnalysis of the 2006 Health Behaviour in School-aged Children survey, a cross-sectional study involving schoolchildren aged 10–17 years.SettingSchools in the Republic of Ireland.ResultsThe proportion of children (n3599) engaged in weight reduction behaviour (‘dieting’ among non-overweight students) was 10·3 %. Older children, females and those from higher social classes (SC) were more likely to report such behaviour. Non-overweight schoolchildren who reported weight reduction behaviour were less likely than those not engaged in such behaviour to frequently consume sweets, soft drinks, crisps and chips/fried potatoes (OR from 0·39 (95 % CI 0·17, 0·89) to 0·72 (95 % CI 0·53, 0·99)); were more likely to consume diet soft drinks (OR 1·50 (95 % CI 1·03, 2·18); and were more likely to miss breakfast during the week (OR 0·62 (95 % CI 0·48, 0·80). The risk of subjective health complaints increased (OR from 1·47 (95 % CI 1·13, 1·91) to 1·92 (95 % CI 1·48, 2·49)); as did body dissatisfaction (OR 9·17 (95 % CI 6·99, 12·02)), while perception of health and well-being decreased (OR 0·47 (95 % CI 0·36, 0·61)) to 0·54 (95 % CI 0·41, 0·70)). All analyses were controlled for age, gender and SC.ConclusionsWeight reduction behaviour among non-overweight schoolchildren is associated with considerable risk to physical health and emotional well-being. Since the risks associated with such behaviour varies by weight status, health professionals and researchers need to consider these issues in parallel.