OBJECTIVESThe prevention school diary is distributed each year to children aged between 10 and 11 years old by La Ligue contre le cancer, a French association promoting prevention and research against cancer. While they write their homework in the diary, children can learn about a range of health determinants. This diary promotes health in a fun and educational way, as it integrates drawings made by children about the different themes covered by the diary. This paper aims to present the evaluability assessment of this intervention in Ile-de-France (Paris area), where it is already widely deployed.MATERIAL AND METHODSWe have traced the history of the prevention school diary and assessed how it is currently used in Ile-de-France by leading interviews with county committees of La Ligue contre le cancer. Successive versions of the diary and results of teacher satisfaction surveys were examined. All information collected was integrated into a logic model, which characterizes the main components, actors, and effects of the intervention.RESULTSThe prevention school diary was created in the West of France in the late 90s. It was then implemented in Paris and extended to other counties of Ile-de-France. Currently, six counties collaborate on the production of a common diary. Whereas it only dealt with tobacco consumption at the beginning, the prevention school diary now covers nutrition, physical activity, sun exposure, sleep and screen use, addiction, as well as safety in some counties. Three levels of intervention have been identified, depending on whether or not the distribution of the diary is followed by the production of drawings for the next edition or health education sessions. The expected effects of the prevention school diary have been integrated into a logic model emphasizing children, school, and family level. Outcomes include Capabilities (knowledge and skills), Opportunities, and Motivation to adopt healthy Behaviours, according to the theoretical model of behaviour change COM-B.CONCLUSIONThe evaluability assessment phase enabled us to gain a better understanding of the conditions under which the intervention is deployed, and thus to identify the factors to be considered for a broad assessment of its effectiveness. It is especially important since the intervention is already well established in Ile-de-France.