Objectives: To determine the amount of daily screen time in children 18 months of age and ascertain correlations that may be contributing to excessive screen use. Design: A birth cohort was followed with telephone interviews at 6, 12 and 18 months of age. Information about screen time was collected at 18 months. Setting: Parents were recruited from postnatal wards of 2 major public hospitals and at home visits conducted for new mothers within 4 weeks of birth in South Western Sydney (SWS). Participants: Parents of 500 children with infants 18 months of age residing in SWS. Primary and secondary outcomes: Screen time in infants 18 months of age and associated correlations. Results: A large percentage of children 18 months of age (40%) had screen times >2 hours daily. There were significant associations between more than 2 hours of screen time daily and mothers without a partner (OR 4.32 (95% CI 1.67 to 11.15)); having <3 siblings (no siblings: OR 2.44 (95% CI 1.20 to 4.94); 12 siblings: OR 2.08 (95% CI 1.06 to 4.08)); an employed father (OR 1.96 (95% CI 1.09 to 3.52)); no outdoor equipment at home (OR 1.89 (95% CI 1.08 to 3.34)) and fewer than 5 outings per week (OR 2.08 (95% CI 1.37 to 3.17)). Conclusions: There is emerging evidence that excess screen time in children causes adverse cognitive, developmental and health outcomes. This study has shown that a large proportion of very young children residing in SWS have screen exposures for >2 hours per day. Factors contributing to excess screen time have also been identified in this study; however, a greater understanding of risk factors needs to be ascertained in order to facilitate greater public health efforts to reduce screen exposure.