OBJECTIVES: The study aims at documenting patient preferences as well as physician perceptions on decision making in treatment of castration resistant prostate cancer in Japan. METHODS: Anonymous internet-based survey was conducted for patients and urologists. Prior to the survey participation, consent has been obtained. DMPs assessment questionnaire developed by Bruera E et al (J Clin Oncol. 2001 Jun 1;19(11):2883-5) was utilized after conducting Japanese linguistic validation. Decision making preferences (DMPs) questionnaire were consisted from five possible choices ranging from 1 (patient prefers to make the treatment decision) to 5 (patient prefers the physician to make the decision). The response were tabulated and compared between patients and physicians. In addition, Results were further categorized into “Active” (answers 1 and 2), “Shared” (answer 3), and “Passive” decision making (answers 4 and 5). RESULTS: Data of 103 patients and 125 urologists were assessable. Overall, 3% of patients preferred “the physician to make the decision” and 2% of patients preferred “to make the decision on my own”. The discrepancy between patient and physician were found in answer 3 and 4. Active, Shared, and Passive DMPs were chosen by 42 (40.7%) of 103, 49 (47.6%) of 103, and 12 (11.6%) of 103 patients, and by 52 (41.6%) of 125, 41 (32.8%) of 125, and 31 (24.8%) of 125 physicians, respectively. The majority of patients (91 [88.3%] of 103; 95% CI, 80.7% to 93.2%) preferred a shared approach (SDM) with physicians. Physician who belong to non-cancer specialized hospital predicted patient prefer passive approach more than physician who is working for cancer specialized center CONCLUSIONS: The Majority of patients prefer SDM but still 24% of physician assumes that patients prefer a less shared approach. Patient DMP should be assessed more by asking the patient directly rather than assuming that the level of communication allows the physician to predict a strategy.