行为理论常常被用来更好地理解和改变促进健康的行为以及制定基于证据的干预措施。然而，研究人员常常缺乏如何在临终关怀和面对严重疾病的人群中使用这些理论的知识。需要提供清晰的范例或指南。为了描述如何利用行为理论来了解严重病患人群健康促进行为中的关键因素，本文使用了“与医师开始一次关于临终关怀的对话”作为不可治愈癌症患者的个案范例。我们采用了健康促进的方法。步骤1：我们选择了一种理论。步骤2：我们通过访问目标人群应用和改编了选择的理论，结果得到了一个新的行为模型。步骤3：我们操作该模型的因素。一个专家组检查了内容的有效性。我们在认知上测试了问卷。步骤4：我们进行了一项调查研究，并进行了逻辑回归分析，以确定最重要的因素。步骤1：我们选择了计划行为理论。步骤2：这个理论适用于目标行为，但需要扩展。步骤3：最终问卷包括131个项目。步骤4：态度因素是与与医师开始关于临终关怀的对话这一目标行为最重要的因素相关的。本文描述了应用于特定范例的方法，为对理解和改变严重病患人群中目标行为及其因素感兴趣的研究人员和实践者提供了指导。

Behavioral theories are often used to better understand and change health-promoting behaviors and develop evidence-based interventions. However, researchers often lack of knowledge on how to use these theories in palliative care and people confronted with serious illness. Clear examples or guidelines are needed.To describe how behavioral theories can be used to gain insight into critical factors of health-promoting behavior in seriously ill people, using a case example of "starting a conversation about palliative care with the physician" for people with incurable cancer.We used a health promotion approach. Step 1: We chose a theory. Step 2: We applied and adapted the selected theory by performing interviews with the target population which resulted in a new behavioral model. Step 3: We operationalized the factors of this model. An expert group checked content validity. We tested the questionnaire cognitively. Step 4: We conducted a survey study and performed logistic regression analyses to identify the most important factors.Step 1: We selected the Theory of Planned Behavior. Step 2: This theory was applicable to the target behavior, but needed extending. Step 3: The final survey included 131 items. Step 4: Attitudinal factors were the most important factors associated with the target behavior of starting a conversation about palliative care with the physician.This paper describes a method applied to a specific example, offering guidance for researchers and practitioners interested in understanding and changing a target behavior and its factors in seriously ill people.