Health promotion interventions are often underused by care practitioners and, therefore, are not effective. In this study, we assessed nurses' use of a smoking cessation intervention in Dutch cardiac wards and factors associated with their adherence. Ninety-four of 206 nurses did not fully apply the intervention in daily practice; they did not always provide patients with self-help guides, discuss smoking cessation aids, or provide follow-up care. The significant factors in our integrated change model accounted for 52% of the variance in adherence. Adherence was most likely if nurses consistently used an intervention card, perceived advantages of the intervention, had other nurses around them who used it, and had been involved in decision-making.