Background : Unhealthy lifestyle behavior increases the risk of dementia. Various socio-cognitive determinants of behavior influence whether individuals persist in or alter unhealthy behaviors. Objective : This study identifies relevant determinants of behavior associated to dementia risk. Methods : 4,104 Dutch individuals (40 to 79 years) completed a screening questionnaire exploring lifestyle behaviors associated with dementia risk. Subsequently, 3,065 respondents who actively engaged in one or more unhealthy behaviors completed a follow-up questionnaire investigating determinants of these behaviors. Cross-tables were used to assess the accuracy of participants' perceptions regarding their behavior compared to Dutch lifestyle recommendations. Confidence Interval-Based Estimation of Relevance (CIBER) was used to identify the most relevant determinants of behavior based on visual inspection and interpretation. Results : Among the respondents, 91.3% reported at least one, while 65% reported two or more unhealthy lifestyle behaviors associated to dementia risk. Many of them were not aware they did not adhere to Dutch lifestyle recommendations. The most relevant determinants identified include attitudes ( i.e., lacking a passion for cooking and finding pleasure in drinking alcohol or smoking), inaccurate social comparison perceptions ( i.e., overestimating healthy diet intake and underestimating alcohol intake), and particularly low perceived behavioral control ( i.e., regarding changing physical inactivity, altering diet behavior, and smoking cessation). Conclusion : There is promising potential for reducing dementia risk through lifestyle changes in the Netherlands. Dementia risk reduction interventions are likely to be the most successful if they focus on enhancing accurate perceptions about engagement in unhealthy behaviors, while strengthening perceived control to change these behaviors.