The current review aimed to systematically identify dietary, physical activity and sedentary behaviours in preschool children (4-6 years of age) that are prospectively related to overweight or obesity later in childhood. Prospective studies published between January 1990 and June 2010 were selected from searches in PubMed, EMBASE, PsycINFO, CINAHL and Cochrane Library. Studies examining the prospective association between at least one relevant behaviour measured during preschool period (children aged 4-6 years at baseline) in relation to at least one anthropometric measurement at follow-up (age <18 years) were included. Harvest plots were used to summarize the results and draw conclusions from the evidence. Of the 8,718 retrieved papers, 23 papers reporting on 15 different study samples were included in this review. Strong evidence was found for an inverse association between total physical activity and overweight. Moderate evidence was observed for a positive association between television viewing and overweight. Because of the heterogeneity in the assessed dietary behaviours, insufficient evidence was found for an association between dietary intake or specific dietary behaviours and overweight. These results suggest that interventions aiming to prevent overweight among preschool children should focus on promotion of total physical activity and limitation of screen time and that further research is needed to establish whether and which dietary behaviours are important for obesity prevention in this age group. However, despite the lack of evidence for dietary behaviours from the present review, future interventions may already target specific dietary behaviours that are highly prevalent and for which there a clear rationale as well as preliminary evidence that these behaviours are associated with overweight. © 2012 The Authors. obesity reviews © 2012 International Association for the Study of Obesity.