Behaviour problems in young children are common and are linked to mental and physical health problems, and educational and social difficulties. An important factor that influences the development of behaviour problems is the quality of care that children receive from their caregivers. This study aimed to test if a six-session parenting programme [called Video-feedback Intervention to promote Positive Parenting and Sensitive Discipline (VIPP-SD)] reduced behaviour problems in children aged 1 or 2 years who were showing early signs of behaviour problems (e.g. restlessness, impulsivity, tantrums and aggression). VIPP-SD supports caregivers in responding to their child's communication and behaviour. A total of 300 families participated. All families continued to access usual health-care services (e.g. health visitors and general practitioners), but half of the families were randomly allocated to also receive the VIPP-SD programme. We visited all families when the study started, and at 5 and 24 months to see if the children whose families received VIPP-SD showed fewer behaviour problems. We measured the children's behaviour by completing interviews and questionnaires with their caregivers. We also analysed whether or not VIPP-SD was good value for money compared with existing services. We did this by comparing the cost of all of the standard health and community services that families accessed during their time in the study, taking account of the impact that VIPP-SD had on children's behaviour. The children in the VIPP-SD group had lower levels of behaviour problems following the programme than children whose parents did not receive the programme. On average, VIPP-SD children scored 2 points lower on the main measure of behaviour; an example difference would be tantrums being rated as mild rather than severe. By the 2-year visit, the VIPP-SD children continued to show lower levels of behaviour problems. It is less clear whether or not VIPP-SD is good value for money, as this depends on how much money policy-makers are willing to invest for reductions in behaviour problems. Overall, there is strong evidence that the VIPP-SD programme is effective in reducing behaviour problems in the short term. Most of this benefit appears to be maintained for the following 2 years. However, we are less certain about the long-term effect and the VIPP-SD's value for money.