The purpose of the present study was to examine the lifestyle characteristics and preventive readiness of patients with behavior-related diseases (BRD). These are diseases caused by inappropriate behaviors, and which could be prevented by behavior techniques. The courses of these diseases run without notable subjective symptoms for lengthy periods of times. They are compared with an alternate group of diseases which are characterized by manifest subjective symptoms (DSS). The study was conducted with a standardized questionnaire specially designed for the purpose. A representative sample comprising 137 BRD patients and 199 DSS patients was selected in three regions of South Bulgaria. The BRD patients compared to their DSS counterparts showed a higher average age, a larger percentage of males and a greater dissatisfaction with life. In BRD patients, to a greater extent than in DSS patients, the cause of their dissatisfaction with life was the disease itself. There were no statistically significant differences between the two subsamples in lifestyles or in behavior when ill. In addition BRD patients were less interested in participating in preventive programs. These findings indicate that the effectiveness of preventive programs for BRD patients is largely predetermined by their low level of preventive readiness, and is one of the explanations for the widespread prevalence of these diseases in present-day Bulgaria.