Introduction and objectives: Studies of the early signs characteristic of ADHD later on are sparse. The aim is to study whether prospectively collected information from mothers regarding deviations in their child’s development and behaviour during the first two years of life can predict the risk of ADHD. Methods: In the Danish National Birth Cohort (DNBC) mothers were interviewed about their child’s development and behaviour when the child was 6 and 18 months of age, respectively. Children diagnosed with ADHD in Danish paediatric and child psychiatry departments are registered in the Danish National Patient Register. Thus, it is possible to identify children with ADHD in the DNBC and analyses of the information in DNBC will provide information about signs of ADHD before the age of two years. Results: The analyses are preliminary. In august 2010 the study cohort consisted of 76,441 children; of which 681 children were diagnosed with ADHD at follow-up. Deviations reported by mothers when the child was 6 months did not show any associations to later ADHD diagnosis. Some deviations at 18 months of age reported especially in the language and motor field showed statistically significant increased risk of later ADHD diagnosis. Conclusion: At 6 months of age no associations to ADHD were found, but at 18 months of age some deviations in development were associated with the child later being diagnosed with ADHD.