Adoption of potentially effective preventive interventions often fails. This study aimed to identify factors that determine why midwifery practices decide to use a smoking cessation protocol, using a comprehensive model of both organizational and psychosocial factors. A cross-sectional survey was conducted among representatives of all 446 Dutch midwifery practices, of whom 251 (56%) responded. The results show that adoption of the protocol was facilitated by the presence of practice assistants and impeded by a large proportion of clients of foreign ethnic origin. The most successful information channel was the midwives' professional association. A consistent positive attitude (perceiving a lot of advantages, few disadvantages and a low level of ambivalence) and positive social norms toward using the protocol, a perceived large proportion of midwives who use the protocol and knowledge about the protocol significantly increased the likelihood of adoption. The decision to use the protocol was better explained by personal awareness and motivation factors than by organizational factors.