Introduction: We sought to determine the experiences and preferences of prostate cancer patients related to the process of making their treatment decisions, and to the use of decision support.Methods: Population surveys were conducted in four Canadian provinces in 2014–2015. Each provincial cancer registry mailed surveys to a random sample of their prostate cancer patients diagnosed in late 2012. Three registries’ response rates were 46–55%; the fourth used a different recruiting strategy, producing a response rate of 13% (total n=1366).Results: Overall, 90% (n=1113) of respondents reported that they were involved in their treatment decisions. Twenty-three percent (n=247) of respondents wanted more help with the decision than they received and 52% of them (n=128) reported feeling wellinformed. Only 51% (n=653) of all respondents reported receiving any decision support, but an additional 34% (n=437) would want to if they were aware of its existence. A quarter (25%, n=316) of respondents found it helpful to use a decision aid, a type of decision support that provides assistance to decision processes and provides information, but 64% (n=828) reported never having heard of decision aids; 26% (n=176) of those who had never heard of decision aids wanted more help with the decision than they received compared to 13% (n=36) of those who had used a decision aid.Conclusions: The majority of respondents wanted to participate in their treatment decisions, but a portion wanted more help than they received. Half of those who wanted more help felt well-informed, thus, needed support beyond information. Decision aids have potential to provide information and support to the decision process.